Chemistry_Revision_Package_for_SH1_IP_2011

CHEMISTRY REVISION PACKAGE 2011 SH1 IP STUDENTS

Please complete this revision package during the school holidays. You are reminded to give your answers in clear presentation.

There will be a test (30 min) on the first Chemistry lecture lesson. The topics that will be covered in the test are found in this revision package. (1) Mole Concept and Chemical Calculations (2) Redox Reactions and Calculations (3) Atomic Structure (4) Physical Periodicity (5) Chemical Bonding

 

National Junior College

SH1 H2 Chemistry 2010

Chemistry Revision Package Mole concept Section A: Multiple Choice Questions 1

Which of the following contains 1 mol of the stated particles? A B C D

2

)

M2O MO2 M2O5 M4O5

(

)

(

)

(

)

A mixture of 10cm 3 of methane and 10cm3 of ethane was sparked with excess of oxygen. After cooling to room temperature, the residual gas was   passed with aqueous potassium hydroxide. What volume of gas was absorbed by the alkali? A B C D

4

(

On heating, 0.02 mol of the element  M reacts with 0.025 mol of oxygen gas. What is the empirical formula of the oxide of  M ? A B C D

3

Chlorine molecules in 35.5g of chlorine gas Electrons in 1g of hydrogen gas Hydrogen ions in 1dm 3 of 1mol dm−3 aqueous sulfuric acid Oxygen atoms in 22.4dm 3 of oxygen gas at s.t.p

15 cm3 20 cm3 30 cm3 35 cm3

When the salt (C2H5)4 N+Cl− is treated with hydrogen chloride, a white ionic solid  X  is formed. When  X  is dissolved in water, a 20.0cm 3 sample of the solution requires 24.00cm 3 of 0.100mol dm –3 NaOH for neutralization. Another 20.0cm3 of the solution requires 48.00cm 3 of 0.100mol dm −3 AgNO3 for complete precipitation of chloride as AgC l . What do these data show the formula of the anion in  X to be? A B C D

HC12− HC132− HC143− H2C13−

2

 

5

National Junior College

SH1 H2 Chemistry 2010

The reaction of hydrogen sulfide with sulfur dioxide gives sulfur as one of  the product. H2S(aq) S(s) + 2H+(aq) + 2e SO2(aq) + 4H+(aq) + 4e S(s) + 2H2O(l ) How many moles of hydrogen sulfide are needed to react with sulfur  dioxide to produce 1 mol of sulfur? 1 mol A 3 2 mol B 3 3 mol C 2 D 2 mol

6

7

)

(

)

(

)

(

)

Chlorine gas is a serve irritant to the eyes and respiratory system. The maximum save toleration level of chlorine gas in air is 0.005mg dm −3. How many atoms of chlorine are present in 1dm 3 of air at this toleration level? 0.005 23 × 6 × 10 A 71 0.005 23 B × 2 × 6 × 10 71 0.005 1 23 × × 6 × 10 C 71 1000 0.005 1 23 × × 2 × 6 × 10 D 71 1000 3

A sample of 10dm of polluted air is passed through limewater so that all carbon dioxide present is precipitated as calcium carbonate. The mass of  calcium carbonate formed is 0.05g. What is the percentage, by volume, of  carbon dioxide in the air sample? [Relative atomic masses: C, 12.0; O, 16.0; Ca, 40.1; 1 mol of gas under experimental conditions has a volume of 24 dm 3] A B C D

8

(

0.03% 0.05% 0.12% 0.3%

A sample of 2.00g of iron(III) sulfate, Fe 2(SO4)3, is dissolved in water to give 100cm3 of aqueous solution. What is the concentration of SO 42− ions? [Relative formula mass of Fe2(SO4)3 is 400] A B C D

5.00 × 10 −3 1.50 × 10 −2 5.00 × 10 −2 1.50 × 10 −1

mol dm−3 mol dm−3 mol dm−3 mol dm−3

3

 

National Junior College

SH1 H2 Chemistry 2010

Section B: Structured Questions 1.

The mineral phosphorite, Ca 3(PO4)2 exits as phosphate rock in its impure form. Elemental phosphorus can be prepared from phosphate rock using carbon in the   presence of sand, SiO2. The reduction of phosphorite also produces solid Y  and carbon monoxide. Y has the following composition by mass: (i) Ca: 34.2 % Si: 24.5% O: 41.3% Calculate the empirical formula for the solid Y . (ii) Write a balanced equation for the reaction. (iii) A 30.0g sample of phosphate rock was subjected to the above reaction and  produced 5.30g of phosphorus. Calculate the percentage purity of phosphorite in the rock sample.

2.

When potassium chlorate(V), KCl O3, is heated at its melting point, it disproportionates to potassium chlorate(VII), KCl O4, and potassium chloride. Calculate the maximum number of moles of potassium chlorate(VII) which could be  produced from 0.1 mol of potassium chlorate(V).

3.

To identify an oxide of nitrogen, 0.10 mol of the oxide is mixed with an excess of  hydrogen and passed over a catalyst at a suitable temperature.  N xO y

H2(g) catalyst

x NH3

+

 yH2O

The water produced weighs 7.20g. The ammonia produced is neutralised by 200cm 3 of 1.0 mol dm –3 HCl . Find the formula of the oxide of nitrogen. 4.

The percentage by mass of carbon, hydrogen and oxygen in compound T are 60.9%, 4.3% and 34.8% respectively. Determine the molecular formula of  T  given that it has a relative molecular  (i) mass of 138. 3 (ii) 0.520g of  T  was sparked with excess 800cm of oxygen and the water vapour   produced was collected through condensation at room conditions. (a) Write a balanced chemical equation for the complete combustion of  T . (b) What is the volume of water that can be collected?

5.

Combustion of ethane results in the formation of a mixture of carbon dioxide and carbon monoxide in the ratio of 98: 2, together with water vapour. Calculate the volume of oxygen consumed when 4.0g of ethane is burnt at room conditions.

6.

10.0cm3 of an acid  A of concentration 0.0690mol dm −3 reacted completely with 18.40cm3 of a 0.075mol dm −3 NaOH solution. What is the basicity of acid  A?

*7.

A 1.00g sample of a metal  X  (that is known to form  X 2+ ions) was added to 0.100dm3 of 0.500mol dm −3 sulfuric acid. After all the metal has reacted, the remaining acid required 33.40cm3 of 0.500mol dm −3 sodium hydroxide solution for  neutralisation. Calculate the molar mass of the metal and identify the element.

4

 

National Junior College

SH1 H2 Chemistry 2010

*8.

4.30g of an impure sample of ammonium chloride was warmed with 100.0cm 3 of  1.00mol dm −3 sodium hydroxide solution. The mixture was boiled until all the ammonia was driven off. The excess sodium hydroxide in the mixture required 50.00cm3 of 0.250mol dm −3 sulfuric acid for neutralisation. Calculate the percentage purity of the ammonium chloride sample.

*9.

A household cleaner contains ammonia. A 25.37g sample of the cleaner was dissolved in deionised water and made up to 250cm 3 in a volumetric flask. A 25.0cm3 portion of this solution required 37.30cm 3 of 0.360mol dm −3 sulfuric acid for neutralisation. What is the percentage by mass of ammonia in the cleaner?

10.

What volume of carbon monoxide is produced from the reaction of 1.00kg of octane and 1.00kg of oxygen? Assume that 1 mol of gas occupies a volume of 24dm 3 at room temperature and pressure.

11.

Aluminium reacts with manganese(II) oxide to form aluminium oxide and manganese metal. A mixture containing 110g of aluminium and 200g of manganese oxide was heated in a reaction vessel. Which reactant was in excess and how much excess reagent was left? What is the total mass of the mixture at the end of the reaction?

12.

An impure sample of Na 2SO4 has a mass of 1.65 grams and is dissolved in water. Addition of BaCl 2 solution produced a precipitate of barium sulphate with mass 2.32 grams. What is the percentage of Na 2SO4 in the impure sample?

13.

Magnesium metal burns in oxygen gas forming magnesium oxide. What mass of oxygen reacts with 20.0g of magnesium metal? (i) (ii) What is the mass of magnesium oxide formed when 35.0g of magnesium metal is burned in excess oxygen gas?

5

 

National Junior College

SH1 H2 Chemistry 2010

Redox Section A: Multiple Choice Questions 1

In which of the following substances does sulfur exhibit its highest oxidation state? A B C D

2

)

1 2 4 5

(

)

(

)

(

)

A sample of 10.0cm3 of 0.10mol dm −3 iron(II) sulfate solution is titrated against 0.025mol dm −3 potassium manganate(VII) in neutral medium. It is found that 10.0cm3 of the manganate(VII) solution is required to oxidize the iron(II) to iron(III) ions to reach the end-point. What is the oxidation number of the manganese at the end-point? A B C D

4

(

In an experiment, 50cm 3 of a 0.1mol dm −3 solution of a metallic salt reacted exactly with 25cm3 of 0.1mol dm−3 aqueous sodium sulfite. The half-equation for oxidation of sulfite ion shown below. SO32− (aq) + H2O (l ) → SO42− (aq) + 2H+ (aq) + 2e Given that the original oxidation number of the metal in the salt was 3, what would be the new oxidation number of the metal at the end of the reaction? A B C D

3

S8 SO2  Na2S2O3  Na2S4O6

+6 +4 +3 +2

25.0cm3 0.200mol dm −3 of aqueous Fe 3+ solution was found to react completely with 25.0cm3 of 0.100mol dm −3 hydroxylamine, NH2OH. Which of the following could be the nitrogen containing product in this reaction where Fe3+ assumes the role of an oxidizing agent? A B C D

 NO  N2O  NH3 HNO3

6

 

National Junior College

SH1 H2 Chemistry 2010

Section B: Structured Questions 1.

Determine the oxidation number for the underlined elements in each of the following species. (a) SO3 (f) HBrO (g) Na2S4O6 (b) (NH4)2SO4 (c) As4 (h) K 2O2 (d) Fe3O4 (i) CH4 (e) COCl 2 (j) CH3OH

2.

Which of the following equations represent a redox reaction? Identify the oxidizing agent and reducing agent where applicable. (a) 2Al (s) + 3Cl 2(g) → 2Al Cl 3(s) (b) 2Cu2+(aq) + 4I – (aq) → 2CuI(s) + I2(aq) (c) C2H4(g) + H2(g) → C2H6(g)

3.

Determine the oxidation number of the named element in the following reactions. Identify the role of the element and type of reaction where applicable. (a) Phosphorus in P 2O5 + 3H2O → 2H3PO4 (b) Iodine in IO3− + 2I− + 6H+ + 6Cl − → 3ICl 2− + 3H2O (c) Chlorine in NaCl O3 + 2HCl → Cl O2 + ½Cl 2 + NaCl + H2O (d)  Nitrogen in 2H + + 2NO2− → NO + NO2 + H2O

4.

Write balanced half equations and the overall equation for each of the following reactions in acidic medium. (a) S2O32− + I2 → I− + S4O62− (b) Cr 2O72− + Fe2+ → Cr 3+ + Fe3+ (c) IO4− + I− → I2 (d) Cl O3− + Cr 3+ → Cl O2 + Cr 2O72− (e) MnO4− + Cl O− → Mn2+ + Cl O4− (f) FeC2O4 + Ce3+ → Ce2+ + Fe3+ + CO2 (g) C6H5CH3 + MnO42− → Mn2+ + C6H5COOH

5.

Write balanced half equations and the overall equation for each of the following reactions in alkaline medium. (a) I2 + OH− → IO3− + I− (b) I− + MnO4− → I2 + MnO2 (c) Cl O− → Cl − + Cl O3− (d) Cl O− + Mn(OH)2 → Cl − + MnO2 (e)  NO3− + Al + OH− → NH3 + Al (OH)4−

6.

Write a redox equation for each of the following reactions. When aqueous potassium iodide, KI, is added to acidified hydrogen (a)  peroxide, H 2O2, a brown solution of iodine is observed. (b)

When sodium sulfite, Na 2SO3, is added to acidified potassium dichromate(VI), K 2Cr 2O7, the orange solution turns to green Cr 3+ ions.

7

 

National Junior College

SH1 H2 Chemistry 2010

7.

Sodium peroxide, Na 2O2, is used in submarine for absorbing atmospheric carbon dioxide and regenerating oxygen. The reaction produces sodium carbonates as a by-product. Write a balanced chemical equation for this reaction.

8.

A 1.58g piece of iron wire was dissolved in 250cm 3 of sulfuric acid and was converted into iron(II) ions. 25.0cm 3 of this solution was titrated against acidified potassium dichromate(VI) solution of concentration 1.64 × 10 2mol dm 3. Given that 27.30 cm 3 of dichromate(VI) solution were required for this titration, calculate the percentage purity of the iron wire. −

−

9

A solution of aqueous hydrogen peroxide is diluted 20 times and 25.0cm 3 of  this solution required 21.32cm 3 of 0.025mol dm 3 KMnO4 for complete reaction in acidic condition. What is the original concentration of aqueous hydrogen peroxide? −

10. Iodate(V) ions react with iodide ions in the presence of acid to produce iodine: IO3 + 5I + 6H+ → 3 I2 + 3 H2O −

−

1.01g of potassium iodate(V) were dissolved and made up to 250 cm 3 solution. To a 25.0 cm3  portion, an excess of potassium iodide and dilute sulfuric acid was added. The solution was titrated with a solution of sodium thiosulfate, with starch indicator added near the end-point. 29.80cm 3 of thiosulfate solution was required for complete reaction. Calculate the concentration of the thiosulfate solution.

8

 

National Junior College

SH1 H2 Chemistry 2010

Atomic structure Section A: Multiple-Choice Questions 1.

The 68Ge isotope of the Group IV element germanium is medically useful  because it undergoes a natural radioactive process to give gallium isotope, 68 Ga, which can be used to detect tumours. This transformation of  germanium occurs when an electron enters the nucleus, changing a proton into a neutron. Which statement about the composition of an atom of the gallium isotope is correct ? A B C D

2.

It has 37 neutrons. Its proton number is 32. It has a total of 32 electrons. It has 4 electrons in its outer shell.

Which of the following concerning

3.

79 34

Se is smaller than

B

79 34

Se has more neutrons per atom than

C

79 34

Se has more protons per atom than 79 34

Se and

79 35

79 35

)

(

)

(

)

(

)

Br is true?

Br. 79 35 79 35

Br.

Br.

Br contain the same number of electrons per atom.

Which one of the following ions has more electrons than protons and more protons than neutrons? [H = 11 H  ; D = 12 H  ; He = 24 He ; O = 168O ] A B C D

4.

Se and

A

D Both

79 35

79 34

(

D− He+ OH− D3O+

Which atom has three unpaired electrons? A B C D

Al  Co Cr  Sc

9

 

5.

National Junior College

SH1 H2 Chemistry 2010

The diagrams below show the electron arrangement in the outer shells of  five elements, P to T . All elements are from Period 3 of the Periodic table. Element Valence Electronic Configuration

 

ns2np4

P

Q

ns2np5

ns2np1

R

ns2

S

T 

ns2np3

Which of the following statements about the elements  P to T is correct? A B C D 6.

1s2 2s2 2p6 3s2 1s2 2s2 2p6 3s2 3p2 1s2 2s2 2p6 3s2 3p4 1s2 2s2 2p6 3s2 3p6

(

)

 Na, Mg Sr, Ca P, N Cl , Br

(

)

(

)

(

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The valence electronic configuration of elements X and Y are s2 p4 and s2 p2 respectively. X and Y are likely to form a compound of formula A B C D

9.

)

In which of the following pairs is the radius of the second atom greater  than that of the first atom? A B C D

8.

(

What is the electronic configuration of the atom of the element which is isoelectronic with H2S? A B C D

7.

 P will form an ion with +2 charge.  P and S form ions with similar electronic configuration.  R, S are metals while P , Q and T are non-metals.  S and Q will form an ionic compound with a formula of  S 2Q.

 XY   XY 2  X 2Y   X 2Y 3

What is the maximum number of atomic orbitals in the principal quantum number n = 4? A B C D

4 8 9 16

10

 

National Junior College

SH1 H2 Chemistry 2010

Section B: Structured Questions 1.

The table below gives information about the atomic structures of six particles.

Protons Neutrons Electrons

U 13 24 13

V 13 23 10

Particles W X 17 17 20 18 17 18

Y 20 20 18

Z  20 21 20

Which of the above particles are atoms? Explain your answer. Which of the above particles are ions? Identify species which are isotopic, (i) isotonic and (ii) (iii) isoelectronic   Note: isotonic species have same number of neutrons but different number of   protons

(a) (b) (c)

(d) (e)

Suggest and explain the relative size of the isoelectronic species. Derive the chemical formulae for the compounds formed between particles X and Y , (i) (ii) particle V and oxygen.

2.

Magnesium has a relative atomic mass of 24.3. (a) Explain what is meant by the above statement. (b) Define, by means of an equation, the second ionisation energy of  magnesium. Give the electronic configuration of magnesium and draw the (c) corresponding schematic diagram. Draw the shapes of the orbitals that electrons in Mg 2+ ion would occupy (d) in the ground state. Draw the dot-and-cross diagram for the compound formed between (e) magnesium and fluorine.

3.

State the chemical formulae of the following compounds. (a) Sodium sulfite Cacium nitrate (b) Magnesium oxide (c) (d) Iron(III) oxide Ammonium phosphate (e)

11

 

4.

National Junior College

SH1 H2 Chemistry 2010

Beams of particles travelling at the same speed from different sources are subjected to an electric field as shown in the diagram below. A beam of neutrons has already been drawn.

(a)

Sketch on the above diagram how beams of each of the following  particles are affected by the electric field: protons, (i) (ii) electrons, 2 (iii) 1 H  Label each of the beams. +

(b)

Explain the underlying principle that results in the positions and shape of  each beam you have sketched in the above diagram.

12

   ”   s   e   s   a   e   r   c   e    d    “  ,    ”   s   e   s   a   e   r   c   n    i    “  ,    ”    t   n   a    t   s   n   o   c    “   :   s    d   r   o   w   g   n   s    i    d   w   n    l   o   e    l   r   o    T    f   e   c    h    i    t    d   o    f    i   o   r   e   e    P   n   o    l   a    h   y   c    t    i    t    i    i   s   w   c    i   y   s    d   h    k   o    P   n    i    f   a   r   o    l   e    b    P   y   e    l   r    h   a   a    t   c   m    i   n   s    i   y   m    l    h   u    l    i    P   S    F

Section A: Multiple Choice Questions 2 2 5 1. The electronic configurations of atoms of elements G and H are 1s 2s 2p and 1s22s22p6 respectively. Compare the fifth and sixth ionization energies of G and H .

A B C D 2.

3.

4.

5.

6.

5th I.E. G  H

6th I.E. G > H  G  H  G