Anderson STPM Trial Chemistry P2 With Answer

SULIT 962/2

ANDERSON SCHOOL IPOH PERAK PEPERIKSAAN PERCUBAAN STPM TAHUN 2010 NAME : ______________________

FORM : ____________

SUBJECT

: CHEMISTRY PAPER 2 STRUCTURE AND ESSAY

FORM

: UPPER SIX

TIME

: TWO AND A HALF HOURS (21/2 HRS)

DO NOT OPEN THIS QUESTION PAPER UNTIL YOU ARE TOLD TO DO SO.

INSTRUCTIONS 1. Answer all questions in SECTION A in the spaces provided. 2. Answer any 4 question from SECTION B. 3. All workings should be shown. For numerical answers, units should be quoted whereve appropriate. A Data Booklet is provided. This question paper consist of printed pages andblank pages. Prepared by

Approved by

________________ Pn Margaret PK

__________________

1

SECTION A [ 40 marks ] Answer all questions in this section. 1

(a)

Selenium , Se, is in Group 16 of the periodic table and occurs in nature as a mixture of six having the relative abundances given below : Nucleon (mass) number % abundance 74 0.9 76 9.0 77 7.6 78 23.5 80 49.8 82 9.2 Calculate the relative atomic mass , A r , of selenium to three significant figures.

_____________________________________________________________________________________ _____________________________________________________________________________________ [2] (b) Predict the number of neutrons in the most abundant isotope of selenium and write down electronic configuration of the selenium atom. _____________________________________________________________________________________ _____________________________________________________________________________________ [2] (c)

How would you expect the first ionization energy of selenium to compare with that of (i) sulphur and (ii) bromine ? Give your reasoning. (i) ____________________________________________________________________________ ______________________________________________________________________________ _______________________________________________________________________________ (ii) ____________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ [4]

(d)

Selenium dioxide, SeO 2 , is a solid that melts at 315 0C and does not conduct electricity wh molten. State the type of bonding and structure you would expect to find in crystalline sel dioxide. _______________________________________________________________________________ ____________________________________________________________________________[2] 2

2. (a)

The following diagram shows the apparatus needed to measure the standard electrode po copper.

(i)

What do you understand by the term standard electrode potential ?

_____________________________________________________________________________________ _________________________________________________________________________________ [2] (ii)

In the spaces below, identify or describe what the three letters A – C represent .

A:

______________________________________________________________________

B:

______________________________________________________________________

C:

______________________________________________________________________ [3]

(b)

A student wishes to measure the standard electrode potential of the Fe 3+ / Fe 2+ electrode. I space below, draw and label the set up for the right hand beaker that would replace the on in the diagram above.

(c)

Predict how the E of the Fe (i)

3+

/ Fe

2+

electrode would vary as

[2]

the [Fe 3+] is increased ,

____________________________________________________________________________ 3

(ii)

the [ Fe 2+ ] is increased .

_________________________________________________________________________[1] (d)

An aqueous solution of iron (III) chloride is used to dissolve the excess of copper metal fro printed circuit boards. Use the half equations and E 0 values in the data booklet to (i) write an equation for this reaction, ___________________________________________________________________________ (ii)

Calculate the E 0cell for the reaction.

__________________________________________________________________________ [2] 3.

The boiling points of the halogens chlorine, bromine and iodine are shown below: Halogen Chlorine Bromine Iodine

(a)

Boiling points , 0C -35 59 184

Explain this trend in the boiling points of the halogens.

______________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ __________________________________________________________________________________[2] (b)

Iodine reacts with water as shown below. I 2(s) + H 2O (l)

IO - (aq)

+

2H + (aq)

+

I - (aq)

Determine the changes in the oxidation number of iodine in this reaction and comment on answer. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ [2]

4

(c)

A student carries out the following investigation. Step 1 : The student adds an excess of chlorine gas to an aqueous solution of potassium b Step 2 : The student adds aqueous silver nitrate to the resulting solution. (i)

In step 1, what would the student observe? Write an ionic equation for the reaction that takes place.

Observation : _________________________________________________________________ Ionic equation : ________________________________________________________________ [2] (ii)

For step 2 , write the ionic equation, including state symbols for the reaction that ta place.

________________________________________________________________________ [1] (d)

Many covalent compounds of the halogens such as CCl4 , have polar bonds. Polarity can explained in terms of electronegativity. (i) Explain what is meant by electronegativity.

_____________________________________________________________________________________ _____________________________________________________________________________________ [1] (ii) Molecules of the covalent compound, CCl 4 have polar bonds. Draw a diagram to show the shape of the molecule, CCl 4. On your diagram, show the polarity of the bonds.

(iii)

A molecule of CCl 4 is non polar. Explain why.

[1]

_________________________________________________________________________________ _________________________________________________________________________________ [1]

5

4 (a)

A section of a polymer has the structure shown below. .

(i)

Circle a repeat unit of this polymer on the diagram above.

(ii)

Deduce the empirical formula of this polymer.

[1]

______________________________________________________________________ [1] (iii)

Draw a structure for a monomer from which this polymer could be made.

[1] (b)

Proteins are natural polymers made from ά amino acids, such as glycine , H 2NCH 2COOH (i)

Name the functional group made during amino acid polymerization and draw its dis formula. Name of functional group : ________________________________________ Displayed formula of functional group:

(ii)

Name this type of polymerization .

[2]

_______________________________________________________________________ [1] (iii)

Draw a displayed formula for the dipeptide H, C 4H 8N 2O 3, made from glycine, H 2NCH 2COOH.

[1] 6

(iv)

A student made 1.10g of dipeptide H starting from 1.40g of glycine. Calculate the percentage yield obtained. Give your answers to 3 significant figures.

[2] (v)

When glycine is treated with hydrochloric acid a compound J , C 2H 6Cl NO 2 , is forme Draw s structure for compound J.

[1]

=========================================================== SECTION B [ 60 marks ] Answer any four questions in this section.

5 (a)

There are trends in the physical and chemical properties of the oxides of the elements of Using only the oxides of the elements magnesium, aluminium and sulphur, describe and e the trends in Chemical formula Structure and bonding Action of water [ 7]

(b)

Lattice enthalpy is used to compare the strengths of ionic bonds. Define the term lattice enthalpy. Describe and explain the effect of ionic charge and ionic radius on the magnitude of a latt enthalpy. Explain the trend in thermal decomposition of the carbonates of Group 2 [ 8] elements.

6.(a)

The kinetics of the reaction 2NO (g) +

Br 2 (g)

2NOBr (g)

ΔH = -23 kJ mol -1

are second order with respect to [ NO ] and first order with respect to [ Br 2 ] . The reactio activation energy of + 5.4 kJ mol -1 (i) Write the rate equation for the reaction and state the units of the rate constant. (ii) Sketch and label a reaction pathway diagram for the reaction showing all relevant e changes. [4] (b)

(i)

A bromoalkane, Rbr, is hydrolysed by aqueous sodium hydroxide. Write a balance equation for the reaction and suggest what type of reaction it is. 7

(ii)

The following results were obtained from two experiments on such a hydrolysis. In e experiment, the overall [ NaOH (aq) ] remained virtually constant at the value given top of the column. Time / min 0 40 80 120 160 200 240

[ RBr ] / mol dm -3 when [ OH - ] = 0.10 mol dm -3 0.0100 0.0079 0.0062 0.0049 0.0038 0.0030 0.0024

[ RBr ] / mol dm -3 when [ OH - ] = 0.15 mol dm -3 0.0100 0.0070 0.0049 0.0034 0.0024 0.0017 0.0012

Plot these data on suitable axes and use your graph to determine the following . I Use the half life method to deduce the order of the reaction with respect to the bromoalkane. II Use the initial rates method to deduce the order of the reaction with respect to sodi hydroxide. III Construct a rate equation for the reaction and use it to calculate a value for the rate constant. (iii) 7. (a)

Based on the answers to b (ii), explain the mechanism of the reaction. [ 11]

The following diagram shows, for different mixtures of liquids A and B, the partial vapou pressures of the two components and the total vapour pressure of the mixture.

Vapour Pressure

100% A

(i) (ii)

vapour pressure

100% B

Explain what this mixture deviates from Raoult’s Law. What is meant by the term azeotrope, and what features of a mixture cause an azeotr [5] form ?

8

(b)

The table below gives information about hydrogen chloride, water and the azeotrope form them. The azeotrope boils at 108.5 0C. Substance Hydrogen chloride Water

Boiling point / 0C 85.0 100.0

Azeotrope composition / % by mass 20.2 79.8

Use this information to construct a liquid-vapour diagram. Use your diagram to show that impossible to separate completely a mixture of these two compounds by [5] distillation. (c)

(i) (ii)

(iii)

8.

(a)

(b)

9.

What is meant by the partition coefficient ? If iodine is shaken with 100 cm 3 of water and 100 cm 3 of an organic solvent, the concentration of iodine in the water layer is 4.0 x 10 -3 moldm -3 and in the organic solvent is 1.0 x 10 -2 moldm -3. Calculate the partition coefficient for iodine between the organic solvent and water. The aqueous layer is separated and shaken with 50cm 3 of the pure organic solvent. will be the concentration of iodine in the organic solvent at equilibrium in moldm–3 [6]

Explain the following observations. (i) An equipment made from iron can be prevented from rusting by connecting th equipment to magnesium. Explain using the information from the data bookle [3] (ii) Explain why the pH of an aqueous solution of ammonium nitrate is less than 7 [4] Give one chemical test that can be used to differentiate the following pairs of compo State the observation and write the equation for the reaction. (i) phenylmethanol and phenol (ii) butan-2-ol and 2 methylpropane-2-ol [8]

Alpha hydroxyl acids (AHA) are used in skin-care products. For effective treatment of the is important that the pH of cosmetics is closely controlled. Products are sold in a buffered with different pH ranges for different uses. Glycolic acid , shown below is used as an AHA in many cosmetics. O HO OH

(a)

glycolic acid

(i)

Deduce the molecular formula of glycolic acid.

(ii)

Glycolic acid is manufactured in two stages: Stage 1 : Chloroethanoic acid. ClCH 2COOH is reacted with aqueous sodium hydroxide. Stage 2 : The resulting solution is acidified. Write equations for each stage in the manufacture of glycolic acid.[ 4] 9

(b)

A glycolic acid skin care product has a buffered pH of 4.4. The buffer contains a solution o glycolic acid and its sodium salt, sodium glycolate. Explain what a buffer is and how this buffer system works. Include equations in your answ Calculate the proportions of glycolic acid and sodium glycolate in this skin care product. Glycolic acid had a K a value of 1.48 x 10 -4 mol dm -3 . [6]

(c)

A chemist investigated compound E , C x H y O z , as a prospective cosmetic for skin care. A sample of 4.362 g of compound E was analysed by burning in oxygen to form 5.119g of and 1.575g of water. Mass spectrometry produced a molecular ion peak at m/e = 150.0. Calculate the molecular formula of E. Show your working. [5]

10.

In aqueous solutions , some organic compounds are bases and some are acids; others are

(a)

(i) (ii)

Identify an organic compound that acts as an acid in water and give an equation to this behaviour. Phenylamine, C 6H 5NH 2 , acts as a base in water . Give an equation for this behaviou Suggest with reason, how the basicity of 3-chlorophenylamine, C, might compare wi that of phenylamine. [6] NH 2

NH 2

Cl

phenylamine (b)

C

The dye D can be obtained from an amine and a phenol under suitable conditions. CH 3 CH 3 -

-N = N -

- OH

Dye D

CH 3

Draw the structural formula of the amine and the phenol used to make D . Describe the rea and conditions required to convert these two compounds to D. [5] (c)

When Benzaldehyde is treated with very concentrated aqueous potassium hydroxide, follo acidification, two compounds , F ( C 7H 8O ) and G (C 7H 6O 2 ) are formed in equimolar amou F and G both evolve hydrogen gas when treated with sodium metal. G dissolves in sodium hydroxide but F does not, G can be obtained from F by treatment with acidified potassium dichromate (VI). Suggest structures for F and G, and explain the reactons they undergo. [ 5 ]

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

10

ANSWERS SECTION A [ 40 marks ] Answer all questions in this section.

1

(a)

(b)

(c)

Selenium , Se, is in Group 16 of the periodic table and occurs in nature as a mixture of six having the relative abundances given below : Nucleon (mass) number % abundance 75 0.9 76 9.0 77 7.6 78 23.5 80 49.8 82 9.2 Calculate the relative atomic mass , A r , of selenium to three significant figures. Ar = 0.9 x 74 + 9 x 76 + 7.6 x 77 + 23.5 x 78 + 49.8 x 80 + 9.2 x 82 = 79.1 100 [2] Predict the number of neutrons in the most abundant isotope of selenium and write down electronic configuration of the selenium atom. No of neutrons : 80 – 34 = 46 Atomic no of 80 Se = 34 2 2 6 Configuration : 1s 2s 2p 3s 2 3p 6 3d 10 4s 2 4p / [4 Ar ] 3d 10 4s 2 4p 4 [2] How would you expect the first ionization energy of selenium to compare with that of (i) sulphur and (ii) bromine ? Give your reasoning. (i)

1 st I. E. of Se is lower / less endothermic than S . Reason : Se and S in the same group, Se is larger than S, greater screening effect, easier to lose the electron.

(ii)

1 st I. E. of Se is lower / less endothermic than Br . Reason : Both in the same period . Br has more protons, size is smaller, valence e more tightly bound in Br [4]

(d)

Selenium dioxide, SeO 2 , is a solid that melts at 315 0C and does not conduct electricity wh molten. State the type of bonding and structure you would expect to find in crystalline sel dioxide. [2] Bonding : covalent bond between Se and O Structure : Giant molecular structure similar to SiO 2

2. (a)

The following diagram shows the apparatus needed to measure the standard electrode po copper.

11

(b)

(i)

What do you understand by the term standard electrode potential ? The electrode potential of an electrode measured against the standard hydrogen electrode at std conditions ( 1 atm, 25 0C and concentration 1 mol dm [2] -3 )

(ii)

In the spaces below, identify or describe what the three letters A – C represent .

A:

Voltmeter / Potentiometer

B:

Salt bridge / KNO 3

C:

1 mol dm -3 H + / H 3O + / HCl / HNO 3 / ½ mol dm -3 H 2SO 4

A student wishes to measure the standard electrode potential of the Fe 3+ / Fe 2+ electrode. I space below, draw and label the set up for the right hand beaker that would replace the on in the diagram above.

- - - - - - - - - - - -

(c)

[3]

Predict how the E of the Fe (i)

3+

/ Fe

2+

Pt electrode solution containing Fe 2+ / Fe 3+ ion at 1 mol dm -3

electrode would vary as

[2]

the [Fe 3+] is increased ,

E 0 increases / becomes more positive ii)

the [ Fe 2+ ] is increased .

E 0 decreases / becomes more negative

[1] 12

(d)

An aqueous solution of iron (III) chloride is used to dissolve the excess of copper metal fro printed circuit boards. Use the half equations and E 0 values in the data booklet to (i) write an equation for this reaction, 2 Fe 3+ (aq) + Cu (s) 2Fe 2+ (aq) + Cu 2+ (aq) (ii)

Calculate the E 0cell for the reaction.

E cell = ( 0.77 – 0.34 ) = + 0.43 V 3.

[2]

The boiling points of the halogens chlorine, bromine and iodine are shown below: Halogen Chlorine Bromine Iodine

(a)

Boiling points , 0C -35 59 184

Explain this trend in the boiling points of the halogens.

Down the group , no of e shells increases, stronger van der Waals forces / intermolecular forces . Greater force is needed to break the intermolecular force , so, b. p. increases. [2] (b)

Iodine reacts with water as shown below. I 2(s) + H 2O (l)

IO - (aq)

+

2H + (aq)

+

I - (aq)

Determine the changes in the oxidation number of iodine in this reaction and comment on answer. I 2 to IO - = From 0 to +1 ( I 2 is oxidized ) Disproportionation has occurred I 2 to I = From 0 to -1 ( I 2 is reduced ) [2] (c)

A student carries out the following investigation. Step 1 : The student adds an excess of chlorine gas to an aqueous solution of potassium b Step 2 : The student adds aqueous silver nitrate to the resulting solution. (i)

In step 1, what would the student observe? Write an ionic equation for the reaction that takes place.

Observation : Orange / Red / Yellow Ionic equation :

Cl2 (aq) + 2Br- (aq)

2Cl- (aq) + Br2 (aq)

[2] 13

(ii)

For step 2 , write the ionic equation, including state symbols for the reaction that ta place.

Ag + (aq) (d)

+ Cl- (aq)

AgCl (s)

[1]

Many covalent compounds of the halogens such as CCl4 , have polar bonds. Polarity can explained in terms of electronegativity. (i) Explain what is meant by electronegativity.

Attraction of an atom for e in a covalent bond (ii)

[1]

Molecules of the covalent compound, CCl 4 have polar bonds. Draw a diagram to show the shape of the molecule, CCl 4. On your diagram, show the polarity of the bonds.

ClδC δ+

Clδ-

(iii)

Clδ-

Clδ-

A molecule of CCl 4 is non polar. Explain why. The polarities / dipoles cancel each other .

4 (a)

[1] [1]

A section of a polymer has the structure shown below. .

(i)

Circle a repeat unit of this polymer on the diagram above.

(ii)

Deduce the empirical formula of this polymer. C 4H 8 = CH 2

(iv)

[1]

[1]

Draw a structure for a monomer from which this polymer could be made. H CH 3

C = C H

CH 3

[1] 14

(b)

Proteins are natural polymers made from ά amino acids, such as glycine , H 2NCH 2COOH (i)

Name the functional group made during amino acid polymerization and draw its dis formula. Name of functional group : Peptide / amide Displayed formula of functional group: H -C – N – O

(ii)

[2]

Name this type of polymerization .

Condensation (iii)

[1]

Draw a displayed formula for the dipeptide H, C 4H 8N 2O 3, made from glycine, H 2NCH 2COOH. H H O H H O N - C - C - N - C - C H

(iv)

H

H

[1]

O - H

A student made 1.10g of dipeptide H starting from 1.40g of glycine. Calculate the percentage yield obtained. Give your answers to 3 significant figures.

2 H 2NCH 2COOH 2 moles

H 2N-CH 2-CONH-CH 2–

COOH

+

H 2O

gives 1 mol of dipeptide

1.40 = 1.4 x ½ = 9.3 x 10 -3 mols dipeptide 75 75 Mass of dipeptide should be produced = 9.3 x 10 -3 x 132 = 1.232 g % yield = 1.10 / 1.232 x 100 = 89.29% (v)

[2]

When glycine is treated with hydrochloric acid a compound J , C 2H 6Cl NO 2 , is forme Draw s structure for compound J. O + H 3N - CH 2 – C Cl OH

[1]

15

ESSAY ANSWERS Question Explanation Marks 5 (a) Chemical formula of oxides MgO , Al2O 3 , SO 2 , SO 3 1 Number of valence electrons increases from Mg to S / oxidation state of the element increases. 1 Structure and bonding MgO – ionic Al2O 3 – ionic with covalent character / intermediate bonding 1 SO 2 , SO 3 – covalent Stucture MgO - giant structures Al2O 3 1 SO 2 , SO 3 - simple molecules .. 2+ 1 Eg : [ Mg ] [ : O : ] 2.. xx .. xx xx O = S = O xx Action of water MgO reacts with water to give alkaline solution MgO (s) + H 2O (l) Mg(OH)2 (aq)

1

Al2O 3 does not react with water .

1

SO 2 and SO 3 reacts to give an acidic solution. SO 2 (g) + H 2O (l) H 2SO 3 (aq) 5(b)

1 Max 7 Lattice enthalpy is energy released when 1 mol of ionic solid is formed from its gaseous ions . 1 + 1 Lattice enthalpy άq q / charge + r + r radius 1 Higher the charge on the ions, the larger the lattice energy / more exothermic Smaller the size of the ions, larger the lattice energy / more exothermic1 Thermal Decomposition of carbonates Group 2 carbonates - BeCO 3 , MgCO 3 , CaCO 3 , SrCO 3 and BaCO 3 1 MCO 3 (s) MO (s) + CO 2 (g) Down the group, Thermal stability increases 1 1 Reason – size on the cation is getting bigger. - cation not able to polarize the electron cloud of the carbonate ion / - size of the cation (M 2+) increases , causing a decrease in charge 1 density and a decrease in the polarizing power.

Q6 (a)

(i)

Rate = k [ NO ] 2 [ Br 2 ]

1 16

Units for k = mol -2 dm 6 s -1

1

(ii)

2NO (g) + Br 2 (g)

+5.4kJ 2

23 kJ

2 NOBr (g)

Reaction coordinate

6 (b)

(i)

RBr

+

NaOH

R – OH

+

NaBr

Type = nucleophilic substitution.

1 1

(ii) Graph - axes labelled - 2 curves I From the graph 1 st half life = 2 nd half life ( values given) Half life is a constant Reaction is first order with respect to [RBr ]

1 2

1 1

II Initial rates measured from the tangent of both curves when time = 0 Set 1 Set 2

[ OH - ] 0.10 0.15

[ RBr ] 0.010 0.010

Initial rates / mol dm -3 min -1 5.77 x 10 -5 9.62 x 10 -5

1

Rate = k [ OH - ] n [ RBr ] Set 2 Set 1

9.62 x 10 -5 = k [ OH - ] n [ 0.01 ] 5.77 x 10 -5 k [ OH - ] n [ 0.01 ]

n=1 Order with respect to [ OH - ] = 1 ( first order ) III

Rate = k [ OH - ] [ RBr ]

1

1

Using set 1 or set 2 / (students results) k = rate / [ OH - ] [RBr] = 5.77 x 10 -5 / 0.10 x 0.010 = 0.0577 mol -1 dm 3 min -1 6(b)

(iii) SN 2 mechanism

1 1 17

δ+

R - Br δ-

slow

R δ+ ------Br δOH -

fast

R – OH + Br -

Intermediate complex

1

1

Max 15 7 (a)

(i) Mixture shows negative deviation 1 Mixture has a vapor pressure lower than predicted by ideal behavior 1 There is stronger interaction between the two molecules The forces of attraction between A and B are stronger than between 1A and A molecules or between B and B molecules. 1 (ii) Azeotrope is a ,mixture with constant boiling point that produces a vapor 1 with the same composition as the liquid.

7 (b) vapor 85

vapor liquid

liquid

0

108.6 Temp / 0C 100 3

79.8

100%

% of water Sketch = 1 Axes = 1 Correct b. p = 1 When a mixture of any composition is fractionally distilled, for example at 80% water, the vapor will be richer in water and water will be the first distillate 2 followed by the azeotropic mixture. 7 (c)

(i) Partition coefficient is the ratio of the concentration of a solute , X , 1in the two solvents at equilibrium at a fixed temperature, which is a constant. Or K = [ X ] solvent 1 [ X ] solvent 2 (ii)

[ I2 ]

organic layer

= [ 1 x 10 -2 ]

= 2.5

1 18

[ I2 ]

[ 4 x 10 -3 ]

water

(iii) No of mols of I 2 in 100 cm 3 of water = 4 .0 x 10 -3 x 100 1000

= 4.0 x 10 -4 mols

Let x mol of I 2 in 50 cm 3 of solvent , -4 So , [ 4.0 x 10 - x ] mols of I 2 remain in 100 cm 3 of water. So,

[ x x 1000 / 50 ] 0rganic layer = 2.5 [ 4.0 x 10 -4 – x / 100 ] water

1

x

1

So, [ I 2 ] 8 (a)

solvent

= 2.2 x 10 -4 mols

= 2.22 x 10 -4 x 1000 50

(i) Mg 2+ + 2 e = Mg Fe 2+ + 2e = Fe

= 4.44 x 10 3 mol dm -3

E 0 = -2.38V E 0 = -0.44 V

E 0 value of Mg is more negative compared to iron. / Mg is more Electropositive It will undergo oxidation rather than iron Acts as the sacrificial anode (ii) NH 4NO 3 (aq)

1

NH 4+ (aq)

NH 4 (aq) + H 2O (l) +

1 1 1

+ NO 3- (aq) complete ionization

NH 3 (aq)

+ H 3O (aq)

1

+

- NH 4NO 3 is a salt that dissolves / dissociates completely to produce NH 1 4+ ion. - NH 4+ ion acts as a Bronsted Lowry acid. 1 + - donating H to water and producing NH 3 and H 3O ion which makes the 1 solution acidic. 8 (b)

(i) phenyl methanol and phenol Chemical test = FeCl 3 Observation = phenol reacts to form a purple solution Phenyl methanol – no reaction Equation

1 1 1

1 OH

+ FeCl3 r. t.

OH

…..FeCl3

19

(ii) butan-2 ol and 2 methylpropan-2 ol Butan-2 ol = secondary alcohol & 2 methylpropan-2 ol = 3 0 alcohol Chemical test = triiodimethane test or Oxidation using KCr 2O 7 acidified 1 Observation = butan -2 ol produces a yellow precipitate of CHI 3 2 methylpropan- 2 ol shows no reaction /

1 1

Butan-2 –ol is oxidized . Reagent turns green 2 methylpropan- 2 ol shows no reaction Equation

9 (a)

(i)

C 2H 4O 3

1

1

(ii)

3

9(b) 20

3

3

1 Or

pH = pKa - log [ salt ] / [ acid ] 4.4 = - log (11.48 x 10 -4 ) - log [ salt ] / [ acid ] [ salt ] / [ acid ] = 3.72

9 (c)

21

5

10 (a)

(i)

carboxylic acid / phenol / amino acid / named example or correct formula 1 ! equation to give the correct negative ion ! CH 3COOH

(ii)

+

H 2O

C 6H 5NH 2 + H 2 O

CH 3COO (aq) + -

C 6H 5NH 3+ + OH -

H 3O

+

(aq)

1

1

3-chlorophenylamine is a weaker base than phenylamine. 1 1 - chlorine is e withdrawing 1 the - Reduces the availability of the lone pair on nitrogen for donation by inductive effect. 10(b)

Amine CH 3

NH 2

Phenol

CH 3 OH

2

CH 3 22

CH 3

NH 2

CH 3

NaNO 2 / HCl 0–50C CH 3

N ≡ N+ +

CH 3

OH

N ≡ N+

NaOH

D

CH 3 10(c)

F=

G

CH 2OH

COOH

F and G both react with Na. - so both are acids H 2 gas is liberated and salt is formed

1 Condition – 1m 1

2

1

G dissolves in NaOH but F does not . So, G is a carboxylic acid

1

G can be obtained from F through oxidation So, F is a primary alcohol

1

Reaction equations. F

2

CH 2OH + 2Na

Oxidation of F CH 2OH + [O] G

2

K 2Cr 2O 7 H+

COOH + 2Na COOH

+

NaOH

2

CH 2O -Na + + H 2 (g)

COOH

COO - Na + + H 2 (g) COO -Na + + H 2O

23