1 - Stoichiometric Relationships Core WS Ms

 

SDIS DP CHEMISTRY

Topic 1 – Stoichiometric Stoichiometric relaonships WS – CORE 1.

What is the sum of all coecients when the following equaon is balanced using the smallest possible whole numbers?  __ C2H2 + __O2 → __CO2 + __H2O A.

2.

5

B.

7

C.

11

D.

13

3 1.7 g of NaNO3 ( Mr  =  = 85) is dissolved in water to prepare 0.20 dm  of soluon. What is the concentraon of the resulng  –3 soluon in mol dm ?

A.

3.

4.

5.

B.

0.1

C.

0.2

D.

1.0

 –3 23  –1 How many molecules are present in a drop of ethanol, C2H5OH, of mass 2.3 × 10  g? (L = 6.0 × 10  mol )

A.

3.0 × 10

C.

6.0 × 10

19

20

B.

3.0 × 10

D.

6.0 × 10

20

26

Which sample has the greatest mass? A.

1 mol of SO2

B.

2 mol of N2O

C.

2 mol of Ar

D.

4 mol of NH3

The relave molecular mass of a gas is 56 and its empirical formula is CH2. What is the molecular formula of the gas? A.

6.

0.01

CH2

B.

C2H4

C.

C3H6

D.

C4H8

Ethanol is used as a component in fuel for some vehicles. One fuel mixture contains 10 % by mass of ethanol in unleaded petrol (gasoline). This mixture is oen referred to as Gasohol E10. (a)

Assume Assume tthat hat tthe he ot other her 90 90 % by ma mass ss of G Gaso asohol hol E10 E10 is octane octane.. 1.0 1.00 0 kg of th this is fuel fuel mixtu mixture re was b burn urned. ed.

 (i)

CH3CH2OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l)

O  –1 ∆H  = –1367 kJ mol

C8H18(l) + 12

O  –1 ∆H  = –5470 kJ mol

O2(g) → 8CO2(g) + 9H2O(l)

Calc Calcula ulate te the the mass mass,, in g, o off et ethan hanol ol and and o octa ctane ne iin n 1.0 1.00 0 kg of th the e fu fuel el mixt mixture ure.. ........................................................................................................................... ...........................................................................................................................

(ii (ii))

(1 )

Calc Calcula ulate te the the am amoun ount, t, in m mol, ol, of of et ethano hanoll and oct octane ane iin n 1.0 1.00 0 kg o off the fuel fuel mix mixtur ture. e. ........................................................................................................................... ...........................................................................................................................

(1 )

1

 

SDIS DP CHEMISTRY  (iii)

Calcula Calculate te the total total amo amount unt of e energy, nergy, in kJ, re released leased when 1 1.00 .00 kg of the fuel fuel mixtur mixture e is com completely pletely burne burned. d.

ENERGETICS ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................  (b)

(3 )

If the fuel bl blend end wa wass vapori vaporized zed be before fore co combus mbuson, on, pre predict dict whe whether ther th the e amo amount unt of e energy nergy rreleas eleased ed woul would d be greater, less or the same. Explain your answer. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......... ........... ....... ....... ....... ........... ........... ........... ....... ........... ........... ........... ........... ........ ........... ........... ........... ....... ....... ...... ........

7.

(2) (Total 7 marks)

What mass, in g, of hydrogen is formed when 3 mol of aluminium react with excess hydrochloric acid according to the following equaon? 2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g) A.

8.

B.

4.5

C.

6.0

D.

9.0

What is the total number of hydrogen atoms in 1.0 mol of benzamide, C6H5CONH2?

A.

9.

3.0

7

B.

6.0 × 10

23

C.

3.0 × 10

24

D.

4.2 × 10

24

What is the sum of the coecients for the equaon when balanced using the smallest possible whole numbers?  __N2H4(g) + __O2(g) → __NO2(g) + __H2O(g) A.

10.

5

B.

6

C.

7

D.

8

Chloroethene, C2H3Cl, reacts with oxygen according to the equaon below. 2C2H3Cl(g) + 5O2(g) → 4CO2(g) + 2H2O(g) + 2HCl(g) What is the amount, in mol, of H2O produced when 10.0 mol of C2H3Cl and 10.0 mol of O2 are mixed together, and the above reacon goes to compleon? A.

4.00

B.

8.00

C.

10.0

D.

20.0

 

2

 

SDIS DP CHEMISTRY 11.

A xed mass of gas has a certain certai n volume at a temperature of 50 °C. What temperature is rrequired equired to double its volume while keeping the pressure constant? A.

100 K

B.

323 K

C.

373 K

D.

646 K

  12.

 –3 3  –3 3 What is the concentraon of NaCl, in mol dm , when 10.0 cm  of 0.200 mol dm  NaCl soluon is added to 30.0 cm  of  –3 0.600 mol dm  NaCl soluon?

A.

13.

14.

0.300

C.

A.

2 mol of NaOH

B.

1 mol of NH4Cl

C.

2 mol of CaCl2

D.

1 mol of Al2O3

0.500

D.

0.800

 –1 What is the approximate molar mass, in g mol , of MgSO4•7H2O?

120

B.

130

C.

138

D.

246

C.

C4H8

D.

C4H10

Which is both an empirical and a molecular formula? A.

16.

B.

Which amount of the following compounds contains the least number of ions?

A.

15.

0.450

C5H12

B.

C5H10

12 molecules of hydrogen gas, H2(g), and 5 molecules of oxygen gas, O2(g), were mixed together under condions which allowed the reacon to go to compleon, according to the following equaon. 2H2(g) + O2(g) → 2H2O(g)

The following diagram represents the mixture of reactants.

 

Which diagram represents the reacon mixture when the reacon was complete? A.

B.

3

 

SDIS DP CHEMISTRY C.

17.

D.

Brass is a copper containing alloy a lloy with many uses. An analysis is carried out to determine the percentage of copper present in three idencal samples of brass. The reacons r eacons involved in this analysis are shown below. + 2+ Step 1: Cu(s) + 2HNO3(aq) + 2H (aq) → Cu (aq) + 2NO2(g) + 2H2O(l)  – 2+ Step 2: 4I (aq) + 2Cu (aq) → 2CuI(s) + I2(aq)

Step 3: I2(aq) + 2S2O3  (a)  (a)

(i)

2–  – 2– (aq) → 2I (aq) + S4O6 (aq)

Deduce the change in the oxidaon num umb bers of copper and nit nitrogen in step 1. REDOX

Copper: ........................................................................................................................... Ni Nitr trog ogen en:: .. .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... ....  (i  (ii) i)

(2) (2)

Id Iden enf fy y tthe he oxid oxidiz izing ing agen agentt in in sste tep p 1. 1. REDOX ...........................................................................................................................

(1) (b)

A student student carried out tthis his experim experiment ent tthree hree mes mes,, wit with h thre three e idencal idencal small brass nails, and o obtaine btained d th the e following results. Mass of brass = 0.456 g ± 0.001 g

Titre

1

2

3

Inial volume of 0.100 mol dm –3 S2O32– (± 0.05 cm3)

0.00

0.00

0.00

 –3 2– 3 Final volume of 0.100 mol dm  S2O3  (± 0.05 cm )

28.50

28.60

28.40

 –3 2– 3 Volume added of 0.100 mol dm  S2O3  (± 0.10 cm )

28.50

28.60

28.40

 –3 2– 3 Average volume added of 0.100 mol dm  S2O3 (± 0.10 cm )

 (i  (i))

28.50

2– Calcu Calcula late te the avera average ge am amou ount nt,, iin n mol, mol, of S2O3 S2O3  added in step 3.

........................................................................................................................... ........................................................................................................................... ...........................................................................................................................

(2)

...........................................................................................................................

4

 

SDIS DP CHEMISTRY  (ii  (ii))

Calcula Calculate te the the amou amount, nt, in in mol, mol, of of coppe copperr prese present nt in the b bras rass. s. ...........................................................................................................................

(1)

...........................................................................................................................  (ii  (iii) i)

Calcu Calcula late te the the mas masss of ccop oppe perr in th the e bras brass. s. ...........................................................................................................................

...........................................................................................................................  (iv  (iv))

(1)

Calc Calcula ulate te the the pe perce rcentag ntage e by m mass ass of co coppe pperr in the the bra brass. ss. ...........................................................................................................................

(1)

...........................................................................................................................  (v)

The m manu anufact facture urers rs claim claim tthat hat th the e sample sample o off brass brass con contain tainss 44. 44.2 2 % cop copper per b by y mas mass. s. Determine the percentage error in the result. ...........................................................................................................................

(1)

...........................................................................................................................  (c)

With With refe referen rence ce to its m meta etallic llic sstru tructu cture, re, de descr scribe ibe h how ow brass brass con conduc ducts ts el elect ectrici ricity. ty. BONDING ......................................................................................................................................

(1)

......................................................................................................................................

(Total 10 marks)

18.

What is the coecient of Fe3O4 when the following equaon is balanced using the lowest whole numbers?  __ Al(s) + __ Fe3O4(s) → __ Al2O3(s) + __ Fe(s) A.

19.

3

C.

4

D.

5

 –23 3.0 × 10

B.

 –23 5.0 × 10

C.

30

D.

1.8 × 10

Which molecular formula is also an empirical formula? A.

21.

B.

What is the mass, in g, of one molecule of ethane, C2H6?

A.

20.

2

PCl3

B.

C2H4

C.

H2O2

D.

C6H12O6

Which of the following is consistent with Avogadro’s law?

A.

= constant (V , n constant)

B.

= constant (P, n constant)

5

25

 

SDIS DP CHEMISTRY C.

22.

Vn = constant (P, T constant)

D.

= constant (P, T constant)

The percentage by mass of calcium carbonate in eggshell was determined by adding excess hydrochloric acid to ensure that all the calcium calci um carbonate had reacted. The excess acid le was then trated with aqueous sodium hydroxide.

(a)

3  –3 A student ad add ded 2 27 7.20 cm  of 0.200 mol dm  HCl to 0.188 g of eggshell. Calculate the amount, in mol, of HCl

added.

......................................................................................................................................

(1)

......................................................................................................................................

(b (b))

3  –3 Th The e ex exce cess ss ac acid id requ requir ires es 23 23.8 .80 0 ccm m  of 0.100 mol dm  NaOH for neutralizaon.

Calculate the amount, in mol, of acid a cid that is in excess. ......................................................................................................................................

(1)

......................................................................................................................................  (c)

Determine Determine the a amount mount,, in mol, of HC HCll that react reacted ed wit with h the calciu calcium m car carbonate bonate in th the e eg eggshel gshell. l. ...................................................................................................................................... ......................................................................................................................................

 (d)

(1)

State the equao equaon n for the reacon reacon of HC HCll with the calcium carbon carbonate ate iin n the eggsh eggshell. ell. ACIDS AND BASES ......................................................................................................................................

(2)

......................................................................................................................................  (e)

Determ Determine ine th the e amo amount unt,, in mol, mol, of calc calcium ium ca carbo rbonat nate e in the sa sampl mple e of the eggs eggshel hell. l. ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

(2)

...................................................................................................................................... (f )

Calculate the m ma ass and the percentage by mass of calcium carbonate in i n the eggshell sample. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

......................................................................................................................................  (g  ( g)

(3)

Deduce one assumpon made in arriving at the percentage of calcium carbonate in the eggshell sample.

6

 

SDIS DP CHEMISTRY ......................................................................................................................................

(1)

......................................................................................................................................

(Total 11 marks)

23.

6.0 mol of aluminium reacts with oxygen to form aluminium oxide. What is the amount of oxygen, in mol, needed for complete reacon? 4Al(s) + 3O2(g) → 2Al2O3(s) A.

24.

1.5

B.

3.0

C.

4.5

D.

6.0

What is the total number of nitrogen atoms in two mol of NH4NO3?

A.

4

B.

6.02 × 10

23

C.

24 1.20 × 10

D.

24 2.41 × 10

  25.

 –1 On analysis, a compound with molar mass 60 g mol  was found to contain 12 g of carbon, 2 g of hydrogen and 16 g of

oxygen. What is the molecular formula for mula of the compound?

A.

CH2O

B.

CH4O

C.

C2H4O

D.

C2H4O2

D.

Ag

  26.

Equal masses of the metals Na, Mg, Ca and Ag are added to separate samples of excess HCl(aq). Which metal produces the greatest total volume of H2(g)? A.

27.

Na

B.

Mg

C.

Ca

The graph below represents the relaonship between two variables var iables in a xed amount of gas.

Which variables could be represented by each axis?

 x -axis

 

y -axis

A.

pressure

temperature

B.

volume

temperature

7

 

SDIS DP CHEMISTRY

28.

29.

C.

pressure

volume

D.

temperature

volume

3 8.5 g of NH3 are dissolved in H2O to prepare a 500 cm  soluon. Which statements are correct?

I.

NH NH3 3 is the the solu solute te and and H H2O 2O is th the e so solu lu on

II II..

 –3 Th The e ccon once cent ntra rao on no off tthe he so solu luo on n is is 17 g d dm m

III.

 –3 [NH3] = 1.0 mol dm

A.

I and II only

B.

I and III only

C.

II and III only

D.

I, II and III

Consider the following sequence of reacons. RCH3

RCH2Br

RCH2OH

RCOOH

RCH3 is an unknown alkane in which R represents an alkyl group.  (a)

The alkane contains contains 81.7 % by mass mass of carbon. carbon. Det Determine ermine its e empirica mpiricall formula, formula, showing showing your w working. orking.   ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

(3)

...................................................................................................................................... (b)

Equal volumes volumes of carbon carbon dio dioxide xide and tthe he u unknown nknown alkane are fo found und to to hav have e the same mass, meas measured ured to an accuracy of two signicant gures, at the same temperature and pressure. Deduce the molecular formula of the alkane. ...................................................................................................................................... ......................................................................................................................................

(1)

......................................................................................................................................  

(Total 4 marks) 3

30.

3

 –3

300 cm  of water is added to a soluon of 200 cm  of 0.5 mol dm sodium chloride in the new soluon?

A.

 –3 0.05 mol dm

B.

 sodium chloride. What is the concentraon of

 –3 0.1 mol dm

8

 

SDIS DP CHEMISTRY C.

31.

 –3 0.3 mol dm

NaNO3

B.

AgOH

C.

MgO

D.

KOH

D.

C3H6

Which compound has the empirical formula with the largest mass? A.

33.

D.

 –1 The molar mass of a compound is approximately 56 g mol . Which formula is possible for this compound?

A.

32.

 –3 0.2 mol dm

C2H6

B.

C2H4

C.

C2H2

What is the coecient for O2(g) when the equaon for the combuson of 1 mole of pentane is balanced? C5H12(g) + _O2(g) → _CO2(g) + _H2O(g) A.

34.

B.

6

C.

8

D.

1 16 6

What is the maximum mass, in g, of magnesium oxide that can be obtained from the reacon of oxygen with 2.4 g of magnesium? A.

35.

5

2.4

B.

3.0

C.

4.0

D.

5.6

3 3 5 dm  of carbon monoxide, CO(g), and 2 dm  of oxygen, O2(g), at the same temperature and pressure are mixed

together. Assuming complete reacon according to the equaon given, what is the maximum volume of carbon dioxide, 3 CO2(g), in dm , that can be formed? 2CO(g) + O2(g) → 2CO2 A.

36.

3

B.

4

C.

5

D.

7

Which statement about soluons is correct? A.

When When vi vitam tamin in D dis dissol solves ves in fat, fat, vitami vitamin n D is the the ssolve olvent nt a and nd fat fat iiss the the sol solute ute..

B.

In a ssol olu uon on o off Na NaCl Cl in in wa wate ter, r, N NaCl aCl is tthe he ssol olut ute e and and wa wate terr is tthe he ssolv olven ent. t.

C.

An aq aque ueou ouss sol solu uon on co cons nsis ists ts of wa wate terr d dis isso solv lved ed in a sol solut ute. e.

D.

3 The con concen centra traon on of a sol soluo uon n iiss the the amount amount of ssolv olvent ent dissol dissolved ved in 1 dm dm  of soluon.

9

 

SDIS DP CHEMISTRY

37.

Biodiesel makes use of plants’ ability to x atmospheric carbon by photosynthesis. Many companies and individuals are now using biodiesel as a fuel in order to reduce their carbon footprint. Biodiesel can be synthesized from vegetable oil according to the following reacon.

 (a)

Ide Idenf nfy y the organ organic ic fun funco conal nal gr group oup p pres resent ent in b both oth ve veget getable able o oil il and bi biodi odiese esel. l. ORGANIC

(1)

......................................................................................................................................

(b)

For part part of her ex extende tended d ess essay ay inve invesga sgaon on into into the ecien eciency cy of the process process,, a st student udent reacte reacted d a pu pure re sam sample ple of a vegetable oil (where R = C17H33) with methanol. The raw data recorded for the reacon r eacon is below. Mass of oil Mass of methanol Mass of sodium hydroxide Mass of biodiesel produced

= = = =

1013.0 g 200.0 g 3.5 g 811.0 g

The relave molecular mass of the oil used by the student is 885.6. Ca Calculate lculate the amount (in moles) of the oil oi l and the methanol used, and hence the amount (in moles) of excess methanol. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

(3)

...................................................................................................................................... (e)

Calcula Calculate te the the perc percent entage age yiel yield d of b biod iodies iesel el o obta btaine ined d in this pro proces cess. s. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

(2) (f)

When When biod biodies iesel el is co combu mbuste sted d it pro produc duces es car carbon bon d diox ioxide ide.. Explain Explain why why the us use e of bio biodie diesel sel as a fuel fuel doe doess not signicantly contribute to global warming.

10

 

SDIS DP CHEMISTRY ...................................................................................................................................... ......................................................................................................................................

(1) (Total 14 marks) 38.

The percentage of iron(II) ions, Fe

2+ , in a vitamin tablet can be esmated by dissolving the tablet in dilute sulfuric acid

and trang with standard potassium manganate(VII) soluon, KMnO4(aq). During the process iron(II) is oxidized to 2+ iron(III) and the manganate(VII) ion is reduced to the manganese(II) ion, Mn (aq). It was found that one tablet with a mass of 1.43 g required 11.6 cm 3 of 2.00 × 10 –2 mol dm –3 KMnO4(aq) to reach the end-point. (a)

(i)

State the half-equaon for the oxidaon of the iron(II) ions. REDOX

(1)

...........................................................................................................................

(i (ii) i)

 – St Stat ate e th the e ha half lf-e -equ qua aon on ffor or tthe he rred educ uco on n of the the Mn MnO4 O4  ions in acidic soluon. REDOX

(1)

...........................................................................................................................  (ii  (iii) i)

Deduce Deduce the ove overall rall red redox ox equa equaon on for the rea reaco con. n. REDOX

(1)

...........................................................................................................................

 (  (b b)

(i)

Calculate the amount, in moles, of MnO4 – ions present in 11.6 cm3 of 

 –2  –3 2.00 × 10  mol dm  KMnO4(aq).

...........................................................................................................................

(1)

...........................................................................................................................

 (ii)  (ii)

Calcu Calcula late te the am amou ount nt,, iin n mol moles es,, of of F Fe e

2+  ions present in the vitamin tablet.

...........................................................................................................................

(1)

...........................................................................................................................

(i (iii ii))

De Dete term rmin ine e the the perc percen enta tage ge by ma mass ss of Fe2+ ions present in the vitamin tablet. ...........................................................................................................................

(2)

...........................................................................................................................

(Total 7 marks)  39.

What is the number of oxygen atoms in i n one mole of CuSO4•5H2O?

A.

40.

5

B.

9

23

C.

6.0 × 10

B.

5.0 mol of neon atoms

D.

5.4 × 10

24

Which sample has the greatest mass?

A.

6.0 × 10

25  mo  molecules of hydrogen

11

 

SDIS DP CHEMISTRY C.

41.

1.2 × 10

24  at  atoms of silver

D.

2 1.7 × 10  g of iron

3 3 3 What volume of sulfur trioxide, in cm , can be prepared using 40 cm  sulfur dioxide and 20 cm  oxygen gas by the

following reacon? Assume all volumes are measured at the same temperature and pressure. 2SO2(g) + O2(g) → 2SO3(g) A.

42.

2 20 0

B.

40

C.

60

D.

80

Which sample of nitrogen gas, N2, contains the greatest number of nitrogen molecules?

A.

1.4 g N2

C.

1.4 × 10

23  N2  N2 molecules

B.

3 5 1.4 dm  of N2 at 1.01 × 10  Pa and 273 K

D.

1.4 mol N2

  43.

Aspirin, one of the most widely used drugs in the world, can be prepared according to the equaon given below.

(a)

Stat ate e the nam ame es of the three organic funconal groups in aspirin. ORGANIC ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

(b)

(3)

A student student reacte reacted d some some sali salicylic cylic a acid cid wit with h exc excess ess e ethanoi thanoicc anhy anhydride. dride. Impure solid aspirin aspirin was o obtaine btained d by  ltering ltering the reacon mixture. Pure aspirin was obtained obtai ned by recrystallizaon. The following table tabl e shows the data recorded by the student.

 (i)  (i)

Mass of salicylic acid used

3.15 ± 0.02 g

Mass of pure aspirin obtained

2.50 ± 0.02 g

Determ Determine ine the amo amount unt,, in mol mol,, of salicy salicylic lic aci acid, d, C C6H4( 6H4(OH) OH)COO COOH, H, us used. ed. ........................................................................................................................... ...........................................................................................................................

12

 

SDIS DP CHEMISTRY ........................................................................................................................... ...........................................................................................................................

 (ii)

(2)

Calcula Calculate te the the th theor eorec ecal al yi yield eld,, in g, g, of a asp spirin irin,, C6H C6H4(O 4(OCOC COCH3)C H3)COOH OOH..

........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (i (iii ii))

(2)

De Dete term rmin ine e the perc percen enta tage ge yi yiel eld d of pu pure re aspi aspirin rin.. ........................................................................................................................... ...........................................................................................................................

(iv)

(1)

State the nu number mber of sig signican nicantt gur gures es associated associated with th the e mass of pur pure e aspirin aspirin ob obtained tained,, and calcula calculate te the percentage uncertainty associated with this mass. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................

(v)

(2)

Ano Anothe therr student student re repea peated ted th the e experi experimen mentt and obtain obtained ed an ex exper perime imental ntal yiel yield d of 150 %. The te teach acher er checked the calculaons and found no errors. Comment on the result. ........................................................................................................................... ...........................................................................................................................

(1) (Total 11 marks)

44.

Smog is common in cies throughout the world. One component of smog is PAN (peroxyacylnitrate) which consists of 20.2 % C, 11.4 % N, 65.9 % O and 2.50 % H by mass. Determine the empirical formula of PAN, showing your working. ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................

13

 

SDIS DP CHEMISTRY ................................................................................................................................................

(Total 3 marks) 45.

Which non-metal forms an oxide XO2 with a relave molecular mass of 60? A.

46.

 47.

C

N

C.

Si

D.

S

How many oxygen atoms are there in 0.20 mol of ethanoic acid, CH3COOH?

A.

1.2 × 10

C.

3.0 × 10

23

24

B.

2.4 × 10

D.

6.0 × 10

23

24

4.00 mol of a hydrocarbon with an empirical formula of CH2 has a mass of 280 g. What is the molecular formula of this compound? A.

48.

B.

C2H4

B.

C3H6

C.

C4H8

D.

C5H10

 –3 What will be the concentraon of sulfate ions in mol dm  when 0.20 mol of KAl(SO4)2 is dissolved in water to give 100 3

cm  of aqueous soluon? A.

49.

0.2

B.

1.0

C.

2.0

D.

4.0

3 3 The volume of an ideal gas at 27.0 °C is increased from 3.00 dm  to 6.00 dm . At what temperature, in °C, will the gas

have the original pressure? A.

50.

13.5

B.

54.0

C.

327

D.

600

The data below is from an experiment used to determine the percentage of iron present in a sample of iron ore. This 2+ sample was dissolved in acid and all of the iron was converted to Fe . The resulng soluon was trated with a standard  – soluon of potassium manganate(VII), KMnO4. This procedure was carried ca rried out three mes. In acidic soluon, MnO4  

reacts with Fe

2+ 2+ 3+  ions to form Mn  and Fe  and the end point is indicated by a slight pink colour.

tre inial buree reading / cm Final buree reading / cm

3

3

1

2

3

1.00

23.60

10.00

24.60

46.10

32.50

 –1 3.682 × 10

Mass of iron ore / g  –3

concentraon of KMnO4 soluon / mol dm (a) (a)

 –2

2.152 × 10

De Dedu duce ce tthe he b bala alanc nced ed rred edox ox e equ qua aon on for for tthi hiss re reac acon on iin n acidic soluon. REDOX

14

 

SDIS DP CHEMISTRY ......................................................................................................................................

(2)

......................................................................................................................................  (b)

Id Iden enfy fy the the re redu duci cing ng a age gent nt iin n th the e re reac aco on. n. REDOX

(1)

......................................................................................................................................

 (c  (c))

 – Calc Calcula ulate te th the ea amo moun unt, t, in mo mole les, s, of Mn MnO4 O4  used in the traon.

...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

(2)

......................................................................................................................................

 (d)

 –1 Calcula Calculate te the the amoun amount, t, in moles, moles, of Fe Fe prese present nt in in th the e 3. 3.682 682 × 10  g sample of iron ore.

...................................................................................................................................... ......................................................................................................................................

......................................................................................................................................

(2)

......................................................................................................................................

(e)

 –1 Determ Determine ine the per percen centag tage e by mas masss of Fe pres present ent in tthe he 3 3.68 .682 2 × 10  g sample of iron ore.

...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

(2)

......................................................................................................................................

(Total 9 marks) 51.

Which coecients would balance this equaon?  __ MnO2 + __ HCl → __ MnCl2 + __ Cl2 + __ H2O

52.

MnO2

HCl

MnCl2

Cl2

H2O

A.

1

2

1

1

1

B.

1

3

1

1

1

C.

1

4

1

1

2

D.

1

4

1

2

2

3 What volume of carbon dioxide, in dm  under standard condions, is formed when 7.00 g of ethene (C2H4, Mr = 28.1) undergoes complete combuson?

15

 

SDIS DP CHEMISTRY

53.

A.

B.

C.

D.

How many hydrogen atoms are in one mole of ethanol, C2H5OH?

A.

1.00×10

23

B.

3.61×10

24

C.

5.00

D.

6.00

  54.

What is the coecient for H2SO4(aq) when the following equaon is balanced, ba lanced, using the smallest possible integers?  __Mg3N2(s) + __H2SO4(aq) → __MgSO4(aq) + __(NH4)2SO4(aq) A.

55.

1

B.

3

C.

4

D.

7

Air bags in cars inate when sodium azide decomposes to form sodium and nitrogen: 2NaN3(s) → 2Na(s) + 3N2(g) Calculate the amount, in moles, of nitrogen gas produced by the decomposion of 2.52 mol of NaN3(s). A.

56.

B.

2.52

C.

3.78

D.

7.56

3  –3 3  –3 What volume, in cm , of 0.200 mol dm  HCl(aq) is required to neutralize 25.0 cm  of 0.200 mol dm  Ba(OH)2(aq)?

A.

57.

1.68

12.5

B.

25.0

C.

50.0

D.

75.0

0.600 mol of aluminium hydroxide is mixed with 0.600 mol of sulfuric acid, and the following reacon occurs: 2Al(OH)3(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 6H2O(l)  (a)

De Dete term rmin ine e tthe he limi limin ng g rea react ctan ant. t. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................

 (b)

(2)

Calc Calcula ulate te th the e mass mass of Al2( Al2(SO SO4) 4)3 3 prod produc uced ed.. ..................................................................................................................................... .....................................................................................................................................

16

 

SDIS DP CHEMISTRY .....................................................................................................................................

(2)

..................................................................................................................................... (c)

Determ Determine ine the amo amount unt (in mol) mol) o off exce excess ss reactan reactantt tthat hat rem remains ains.. .....................................................................................................................................

(1)

.....................................................................................................................................

(d )

Dene a Brønsted-Lowry  acid  and  and a Lewis base. ACIDS AND BASES Brønsted-Lowry acid ..................................................................................................................................... Lewis base

(2)

.....................................................................................................................................  (e)

H2S H2SO4( O4(aq) aq) iiss a st stron rong g acid. acid. St State ate the the n name ame a and nd th the e formu formula la of a any ny weak weak ac acid. id. ACIDS AND BASES .....................................................................................................................................

(1)

.....................................................................................................................................

(Total 8 marks)   58.

5 A toxic gas, A, consists of 53.8 % nitrogen and 46.2 % carbon by mass. At 273 K and 1.01×10  Pa, 1.048 g of A occupies 3 462 cm . Determine the empirical formula of A. Calculate the molar mass of the compound and determine iits ts molecular

structure. ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................

(Total 3 marks)

Topic 1 – Stoichiometric relaonships WS – CORE – MARK SCHEME 1.

D

 

2.

(a)

6.

(i)

B

 

3.

A

 

4.

B

(10 % 1000 g =) 100 g ethanol and (9 (90 0 % 10 1000 00 g = =)) 900 900 g o oct ctan ane; e;

(ii)

n(ethanol) = 2.17 mol and n(octane) = 7.88 mol;

(ii (iii) i)

Erelea Erelease sed d fr from om eetha thanol nol = (2 (2.17 .17 × 13 1367 67)) = 296 2966 6 (kJ); (kJ); Ereleased from octane = (7.88 × 5470) = 43104 (kJ);

 

5.

D

1

1

17

 

SDIS DP CHEMISTRY 4

total energy released = (2966 + 43104) = 4.61 × 10  (k  (kJ); 3  Award [3] for correct final final answe answer. r. Accept ans answers wers using w whole hole num numbers bers for mol molar ar masses a and nd rounding. rounding. (b)

greater; fewer intermolecular bonds/forces to break / vaporization is endothermic / gaseous fuel has greater enthalpy than liquid fuel / OWTTE ;  M2 cannot cannot be scor scored ed if M1 is inc incorrect. orrect.

2 [7]

7.

D

9.

8.

D

10.

D

11.

A (a) (i) Copper:  Allow zero/nought zero/nought for 0 0..

17.

D

12.

C 0 to +2 / increases by 2 / +2 / 2+;

13.

B

15.

A

14.

D

16.

A

 Nitrogen: +5 to +4 / decreases by 1 / –1 / 1–; +  Penalize missing missing + sign or incorre incorrect ct notation such as 2+ 2+,, 2 or II, once only.

(ii) ii)

 –  nitri itricc acid id/H /HN NO3 / NO3 /nitrate;  Allow nitrogen nitrogen from nitric acid/nitrat acid/nitratee but not ju just st nitrogen nitrogen..

2

1

 –3 (i) 0.100 × 0.0285; 2.85 × 10  (mol);  Award [2]  for  for correct final answer. 2

(b)

(ii)

 –3 2.85 × 10  (m  (mol);

(iii)

 –3 (63.55 × 2.8 .85 5 × 10 ) = 0.181 g;  Allow 63.5.

(iv)

(v)

1

1

39.7 %

1

10/10.2 %;  Allow 11.3 % i.e. percen percentage tage obtain obtained ed in (iv) is u used sed to divid dividee instead o off 44.2 %.

1

  (c)

 Brass has: has: delocalized electrons / sea of mobile electrons / sea of electrons free to move;  No mark for for just “mobile electrons”.

18.

B

 

19.

B

1

[10]  

20.

A

 –3 3  –3 (a) n(HCl)(= 0.200 mol dm  × 0.02720 dm ) = 0.00544 / 5.44 × 10  (m  (mol);

22.

(b)

(d)

21.

D

1

 –3 3  –3 n(HCl) excess (= 0.100 mol dm  × 0.02380 dm ) = 0.00238 / 2.38 × 10  (mol);

 Penalize not not dividing by 1000 o once nce only iin n (a) and (b (b). ). (c)

 

1

 –3 n(HCl) reacted (= 0.00544 – 0.00238) = 0.00306 / 3.06 × 10  (m  (mol);

1

2HCl( 2HCl(aq aq)) + Ca CaCO3 CO3(s) (s) → CaC CaCl2( l2(aq aq)) + H2O(l H2O(l)) + CO2(g) CO2(g) / + 2+ 2H (aq) + H2O(l) + CO2(g); (aq) + for CaCO3(s) → Ca and products. Award [1]  if  Award  [1]   for correct reactants  if this equation correctly balanced.  Award [1 max] for the following equations:

 2HCl(aq) + CaCO3(s) → CaCl2(aq) + H2CO3(aq) 18

 

SDIS DP CHEMISTRY +

2+  2H  (aq) + CaCO3(s) → Ca (aq) + H2CO3(aq)  Ignore state state symbols symbols..

2

 

(e)

(f)

n(CaCO3) = ( n(HCl)) = × 0.00306;  Award [2]  for  for correct final answer.

 –3 = 0.00153 / 1.53 × 10  (mol);

2

 –1  M r(CaCO3) r(CaCO3) (= 40.08 + 12.01 + 3 × 16.00) = 100.09 /100.1 / M  /  M  =  = 100.09 /100.1 (g mol );

 Accept 100. 100.  –1 m(CaCO3)(= nM ) = 0.00153 (mol) × 100.09 (g mol ) = 0.153 (g);

%CaCO3 = 81.4 % / 81.5 %  Accept answers answers in the range 79 79.8 .8 to 81.5 %. Aw Award ard [3]  for  for correct final answer. (g)

3

only CaCO CaCO3 3 reac reacts ts with aacid cid / imp impurit urities ies are inert inert/non /non-bas -basic ic / impu impuritie ritiess do not rreact eact w with ith the acid acid / no nothin thing g else in the the eggshe eggshell ll reacts with acid / no other carbonates;  Do not accept accept “all cal calcium cium carbo carbonate nate rea reacts cts with acid”. 1 [11]

23.

C

25.

D

27.

C

24.

D

26.

B

28.

C

(a (a)) nC = = 6.80 6.80 and nH =  No penalty penalty for using 1 12 2 and 1 1.. 3

29.

(b)

C3H8;

= 18.1;

ratio of 1: 2.67 /1: 2.7; C3H8;

1 [4]

30.

C

32.

A

34.

C

31.

D

33.

C

35.

B

(a) ester;

37.

(b)

(e)

B

1

am amou ount nt of oil = = 1.1 1.144 44 mol; mol; amoun amountt of met methan hanol ol = since three mol of methanol react with one mol of vegetable oil the amount of excess methanol = 6.204 – (3 × 1.144) = 2.808 mol;

= 6.2 6.240 40 mol; mol; 3

(rel (relativ ativee mo molecu lecular lar m mass ass o off bio biodies diesel, el, C C9H36 9H36O2 O2 = 2 296.5 96.55) 5) max maximum imum yiel yield d of b biodi iodiese esell = 3.432 3.432 m mol ol / 1018 1018 g; g;

 percentage  percent age yield = × 100 = 79 79.67 .67 %;  Allow 80 % for percen percentage tage yield yield.. (f)

36.

2

the ca carbon rbon d dioxi ioxide de was absor absorbed bed by plant plantss initia initially lly so th there ere is n no o net inc increas reasee / vege vegetabl tablee oil is no nott a fossi fossill fuel / ve vegeta getable ble oil iiss formed from (atmospheric) carbon dioxide / OWTTE ; 1 [14]

(a)

38.

(i)

2+ 3+  –  Fe  → Fe  + e ; 1

(ii)

 –  +  –  2+ MnO4  + 8H  + 5e  → Mn  + 4H2O;

(iii)

 –  2+ + 2+ 3+ MnO4  + 5Fe  + 8H  → Mn  + 5Fe  4H2O;

1

19

 

SDIS DP CHEMISTRY  –   Accept e instead instead of e .

(b)

(i)

1

 –  amount of MnO4  =

 –4 × 0.0200 = 2.32 × 10  mo  mol;

1

2+  –4  –3  = 5 × 2.32 × 10  = 1.16 × 10  m  mo ol; 1

(ii)

amount of Fe

(iii)

2+  –3  –2 mass of Fe  = 55.85 × 1.16 × 10  = 6.48 × 10  g;

2+  percentagee of Fe  in tablet =  percentag

× 100 = 4.53 %;

2 [7]

39.

D

 

40.

C

 

B

41.

 

D

42.

(a) carb carboxy oxylic lic acid / carb carboxy oxyl; l; este ester; r;  Do not allow allow carbon carbonyl yl / acid / eth ethanoate anoate / for formula(–COO mula(–COOH). H).

43.

aryl group / benzene ring / phenyl;

 (  (b b)

3

(i)  M r(C7H6O3) r(C7H6O3) = 138.13; n =  Award [2]  for  for the correct final answer.

 –2 2.28 × 10  (mol);

2

 M r(C9H8O4) r(C9H8O4) = 180.17; m = (180.17 × 2.28 × 10 –2 =) 4.11(g);  Accept range range 4.10– 4.10–4.14 4.14 Award [2]  for  for the correct final answer.

(ii)

2

(i (iii ii))

(per (perce cent ntag agee yi yiel eld d=  Accept 60–61 60–61 %.

× 10 100 0 =) 60 60.8 .8 %; 1

(iv (iv))

3; (perce (percenta ntage ge unce uncerta rtaint inty y=  Allow 0.8 % 2

(v)

sample sample cconta ontamina minated ted with etha ethanoic noic acid acid / aspi aspirin rin not dry / im impure pure sample; sample;  Accept specific specific examp example le of a syste systematic matic erro error. r. Do not acc accept ept error in reading balance/weig balance/weighing hing scale scale.. Do not acce accept pt  yield greater greater than 10 100 0 %. 1

× 10 100 0 =) 0.80 0.80 %;

[11]

C 20.2 12.01 = 1.68

44.

 

N 11.4 14.01 = 0.814

=2

O 65.9 16.00 = 4.12

=1

H 2.50 1.01 = 2.48

=5

;

=3

;

 No penalty for use of 12 12,, 1 and/or 1 14. 4.  Award [1 max]  if  if the empirical formula is correct, but no working shown.

C2NO5H3;

3 [3]

45.

C

 

46.

B

 

47.

D

 

48.

D

 –  2+ + 2+ 3+ (a) MnO4 (aq) + 5Fe (aq) + 8H (aq) → Mn (aq) + 5Fe (aq) + 4H2O(l) +  [2]  [1]  Award if correctly balanced. Award  for correctly correctly placing H   and H2O.  Award [1 max] for correct balanced equation b but ut with electro electrons ns shown shown.. Ignore state state symbols. symbols.

50.

(b)

Fe

 

49.

C

2

2+ / iron(II);

20

 

SDIS DP CHEMISTRY  Do not accept accept iron. (c)

(d)

(e)

1

 –2  –2  –4 n = 2.152 × 10  × 2.250 × 10 ; 4.842 × 10  (mol);  Award [1] for correct correct volume Award [1] for correct correct calculatio calculation. n.

2

 –  2+  –4  –3 1 mol of MnO4  reacts with 5 mol of Fe ; 5 × 4.842 × 10  = 2.421 × 10  (mol); (same number of moles of Fe in the iron ore)  Allow ECF from part (a) and (c) provid provided ed some me mention ntion of mol molee ratio is state stated. d. 2

2.421 × 10 –3 × 55.85 = 0.1352(g);  Allow ECF from part (d). 2

× 100 = 36.72 %; [9]

51.

C

53.

B

55.

C

52.

D

54.

C

56.

C

(a) 0.600 mol Al(OH)3 ≡ (1.5)(0.600) (1.5)(0.600) mol H2SO4/0.900 mol H2SO4 needed, but only 0.600 mol used;

57.

H2SO4 limiting reactant;2 Some working must be shown in order to score the second point.  (b)

0.2 .20 00 mol Al2( l2(SO SO4 4)3; 68.4 .4((g); 2  Penalize incorrect incorrect un units. its.

(c)

0.200 mol;

1 Use ECF from (a).

(d (d))

+ A Brø Brøns nste tedd-Lo Lowr wry y aaci cid d is is a pro proto ton/ n/H H  don  donor or;;

(e)

H2CO3 an and ccaarbonic ac acid / CH3COOH aan nd et ethanoic aaccid;

A Le Lewi wiss ba base se is an elec electr tron on-p -pai airr do dono nor; r;

2

1

 Accept any any other wea weakk acid and correct for formula. mula. [8] 58.

empirical formula = CN; Working must be shown to get point.  –1  M r = 51.9 (g mol ); :N C ⎯ C N:;

3 [3]

21