From first principles, calculate the molecular weight of camphor.

Given a correctly set thermometer, describe exactly how you would measure the freezing-point of the benzene and of the solution in an experiment of the above type. Draw a diagram of the essential apparatus.

The freezing-points of benzene and of a solution containing 0.6 gm. of acetic acid in 100 gm. of benzene are respectively 5-4 and 5.15° C. What do you conclude from these data?

[H= 1; C = 12; 0 = 16.]

7. Explain fully the meaning of the following terms: (a) balanced reaction; (b) equilibrium constant; (c) degree of ionization; (d) weak electrolyte; (e) dissociation constant; (f) dialysis.

SECTION C

8. Describe the preparation and collection of a few jars of acetylene free from phosphine and hydrogen sulphide. How is acetylene stored in steel cylinders? Explain why this method is adopted.

What are the reactions of acetylene with (a) chlorine, (b) ammoniacal cuprous chloride, (c) alkaline potassium permanganate?

How is acetylene converted into acetic acid?

9. Starting with ethyl benzoate indicate how you could obtain specimens of (a) pure ethyl alcohol, (b) benzoic acid, (c) diethyl ether.

Write the structural formulae of (i) methyl acetate, (ii) ethyl formate. Briefly describe how ethyl formate is prepared.

10. How, and under what conditions, does an alkyl bromide react with (a) potassium hydroxide; (b) ammonia; (c) sodium and ethyl bromide; (d) sodium ethoxide? Compare the reactions, if any, of bromobenzene with these substances.

State how (i) propionic acid, (ii) normal propylamine can be obtained from ethyl bromide.

A 22/II

OXFORD LOCAL EXAMINATIONS GENERAL CERTIFICATE OF EDUCATION

Summer Examination, 1958

Advanced and Scholarship Level

CHEMISTRY, PAPER II

FRIDAY, JUNE 27. TIME ALLOWED-3 HOURS

[Write the number of the paper, A 22/II, on the left at the head of each sheet of your answers in the space provided.

Answer SIX questions, including not more than THREE from Section A and not more than TWO from each of the Sections B and C.

Mathematical tables are provided.]

SECTION A

1. Describe the extraction of bromine from seawater, and give three industrial uses of bromine.

How, and under what conditions, does bromine react with (a) hydrogen; (b) hydrogen sulphide; (c) potassium iodide; (d) potassium hydroxide? Indicate how you would distinguish between bromine and chromyl chloride.

2. Give an account of the production of (a) amorphous silicon; (b) carborundum; (c) silica gel; (d) soda-glass. What do you know of the uses of (b), (c), and sodium aluminium silicate?

3. Describe the production of (a) sodium hydroxide from sodium carbonate, (b) metallic sodium from either sodium chloride or from sodium hydroxide.

How is sodium converted into (i) sodium peroxide, (ii) sodium cyanide, and what are the uses of these compounds?

What are the differences in properties between (1) sodium and potassium carbonates, (2) sodium and potassium bicarbonates, and (3) sodium and potassium sulphates?

4. What is the chief ore of tin and how is the metal obtained from it? For what purposes is tin used?

How, and under what conditions, does tin react with (a) nitric acid, (b) chlorine, (c) potassium hydroxide?

State what is seen when stannous chloride solution reacts with (i) mercuric chloride solution, (ii) hydrogen sulphide. Write equations for the reactions which occur. How does the precipitate obtained in (ii) react with yellow ammonium sulphide ?

SECTION B

5. Explain clearly what you understand by the terms (a) osmosis, (b) semi-permeable membrane, (c) osmotic pressure.

State how osmotic pressure, for solutions of nonelectrolytes, is related to (i) the concentration of the solute, (ii) the temperature. What deduction was made by van't Hoff from these relationships, and what is its importance?

The vapour pressures of an aqueous solution of urea and of water at the same temperature are respectively 740 and 750 mm. Calculate the weight of urea dissolved in 100 gm. of water, if the molecular weight of urea is 60. 6. State and explain what happens when

(a) rhombic sulphur is heated to 100° C.;

(b) white phosphorus is heated in nitrogen to 200° C.;

(c) a little red phosphorus is heated strongly in a narrow glass tube, sealed at one end;

(d) liquid mercuric iodide is cooled to room temperature.

What is the arrangement of the carbon atoms in graphite and in diamond?

7. Explain the following:

(a) Addition of ammonium chloride to a solution of ammonium hydroxide changes the hydroxyl-ion concentration.

(b) Hydrogen sulphide when passed into a solution of zinc sulphate containing dilute sulphuric acid gives no precipitate, but addition of sodium acetate solution then produces a white precipitate.

(c) Addition of sodium carbonate to a solution of phenolphthalein gives a red solution.

(d) Sheet iron coated with tin, if scratched and exposed to damp air, rusts readily.

SECTION C

8. What do you understand by the terms nitration and sulphonation?

Describe the preparation of pure specimens of (a) m-dinitrobenzene from nitrobenzene, (b) sodium benzenesulphonate from benzene.

How would you detect (i) nitrogen in m-dinitrobenzene, (ii) sulphur in sodium benzenesulphonate? Give the reactions which occur in (i).

9. Distinguish between the radicals acetyl, benzyl, and benzoyl.

Describe how acetyl chloride is prepared, and give its physical properties.

State how acetyl chloride reacts with (a) an alcohol, (b) a primary amine, and give one actual example in each case. How is acetic anhydride obtained from acetyl chloride?

10. (a) Deduce the molecular formula and write the structural formulae of the isomeric saturated aliphatic alcohols which contain 60 per cent. of carbon, and give their names.

What substances are formed when these alcohols are oxidized with acidified dichromate? Give their structural formulae.

(b) The vapour density of the diethyl ester of a dicarboxylic acid is 73. What is the structural formula of the ester, and how does it react with 0.880 ammonia? (c) 20 ml. of a solution of urea with excess alkaline sodium hypobromite solution gave 448 ml. of nitrogen at S.T.P. Calculate the weight of urea in 100 ml. of the solution.

[H = 1; = 1; C = 12; N = 14; 0 = 16; 1 gram-mol. of nitrogen at S.T.P. occupies 22.4 litres.]

A 22/III

OXFORD LOCAL EXAMINATIONS

GENERAL CERTIFICATE OF EDUCATION

Summer Examination, 1958

Advanced and Scholarship Level

CHEMISTRY, PAPER III

MONDAY, JULY 7. TIME ALLOWED-3 HOURS

[Write the number of the paper, A 22/III, on the left at the head of each sheet of your answers in the space provided.

Answer ALL THREE QUESTIONS.

The answer to Question 1 should consist of a brief statement of procedure, actual measurements, calculations, and results.

Mathematical tables are provided.]

1. Determine the percentage of ferrous ammonium sulphate, (NH4)2Fe(SO4)2.6H2O, in the mixture A.

Weigh accurately not more than 10 gm. of A. Transfer the solid to a 250 ml. flask containing about 50 ml. of dilute sulphuric acid, dissolve the solid and make the solution up to 250 ml. with distilled water.

Titrate 25 ml. portions of your solution of A with solution B, which contains 3 gm. of potassium permanganate per litre.

2. Analyse C which is a mixture of two metals.