b) State which of the foregoing elements would not oxidize in air even at

high temperature.

c) State which would most readily react with moisture at room temperature. d) State the essentials of Dalton's atomic theory.

e) Name two fundamental laws of chemistry that are explained by the atomic theory and state one of these laws.

PART II

(Answer four questions from Part II. Answers to extra
questions will receive no credit.)

7. a) How would you treat a mixture of finely powdered sodium chloride, calcium carbonate, zinc, and charcoal so as to obtain the first and last

substances pure and dry?

b) How would you test to determine whether a gas is methane or hydrogen? c) Give the tests by which you would recognize sodium sulphate and a nitrate ion.

8. a) Show by equations the formation of zinc sulphate in five different ways. b) Describe the apparatus and method of procedure in the laboratory experiment for determining the percentage of water in crystallized barium chloride.

9. Indicate whether the following statements are true or false:

a) All elements are solids or gases under normal conditions.

b) An increase of temperature has the general effect of decreasing the speed of a chemical reaction.

c) A solution is a homogeneous body whose composition may vary between certain limits.

d) A water solution of salt and a water solution of sugar of the same molecular concentration have the same freezing-point.

e) Water has less energy than the elements into which it is decomposed. 10. If a mixture of acetylene (C2H2) and oxygen, in reacting proportions, is exploded, carbon dioxide and water vapor are produced. Will the total volume of the products be greater or less than that of the original gases if all are at 200° C. and 760 mm.? What are the relative volumes of the two products?

11. a) What is a saturated solution? How would you determine whether a solution is or is not saturated? Describe the procedure in making a “supersaturated" solution.

b) What is the effect of temperature on the volume of gas that can be dissolved by a liquid? Give an example in illustration of this.

(THIS EXAMINATION IS CONTINUED ON PAGE 3)

12. a) How many liters of ammonia could be formed by the complete reaction, under proper conditions, of 15 liters of hydrogen with an ample volume

of nitrogen? All gases are measured under standard conditions of temperature and pressure.

b) Ten liters of a certain gas weigh 11.6 grams at 0° C. and 760 mm. What is the molecular weight of the gas? Is it heavier or lighter than nitrogen? (Atomic weight N 14.)

13. a) Explain why coal tar may be said to be a by-product of the steel industry. Mention three important chemical compounds that are obtained from coal tar.

b) What is meant by the "fixation" of nitrogen? Explain why it is essential for the prosperity of a nation in peace, and for the prosecution of a war, to have such a process at command.

14. a) What raw materials are required for the manufacture of (1) soap, (2) common glass, (3) bleaching powder, (4) aluminum?

b) Explain how electrolysis is used for the refining of metals and give an example.

15. Show by equations how you would treat the following minerals to prepare other substances of commercial importance: calcium phosphate, limestone, sodium nitrate, gypsum, manganese dioxide.

Number and letter your answers to correspond to the questions selected.

No credit will be given for problems on this paper unless the methods of calculation are clearly indicated. Final numerical answers need not be carried beyond one place of decimals.

PART I

(Answer all questions in Part I)

1. Write equations for the following reactions, using formulas throughout. The equations must be properly balanced to receive credit.

a) Cupric chloride and silver nitrate

b) Zinc oxide and sulphuric acid

c) Calcium hydroxide and sodium carbonate

d) Phosphoric acid and ammonium hydroxide

e) Copper and nitric acid

2. a) State the Laws of Conservation of Matter and of Definite Proportions. b) Give a detailed description of a laboratory experiment in which you determined the quantities involved in a chemical reaction, indicating the calculations necessary.

3. a) How many grams of HCl would be required to react completely with 264 grams of ferrous sulphide (FeS)? How many liters of hydrogen sulphide (H,S), measured at 0° C. and 760 mm., would this weight of ferrous sulphide produce?

b) Calculate the percentage of iron in green vitriol (FeSO4 7H2O). (Atomic weights: Fe 56, Cl 35.5, S 32, O 16, H 1. 22.4 liters of hydrogen sulphide at 0° C. and 760 mm. weigh 34 grams.)

4. Describe briefly the contact process for the manufacture of sulphuric acid. Write three equations involved in the process. How is the test for a sulphate ion made? What property of sulphuric acid (a) makes it useful in the preparation of other acids, (b) makes it useful in the preparation of sulphur dioxide, (c) makes it char paper?

5. Mention by name and formula the substances required for a laboratory preparation of each of the following: (a) nitric acid, (b) ammonia, (c) chlorine. Describe briefly the procedure in the laboratory preparation and collection of one of the foregoing substances.

6. a) Explain why a thin iron wire can be easily burned in oxygen but not in air. b) Does iron burn with a flame?

c) What is formed if iron oxide is heated in a stream of hydrogen?

d) What kind of a chemical change does the iron oxide undergo in (c)?

e) Mention two metals which iron will displace from solutions of their salts.

(THIS EXAMINATION IS CONTINUED ON PAGE 2)

PART II

(Answer four questions from Part II. Answers to extra questions
will receive no credit.)

7. Name three elements that can be obtained in different allotropic forms and describe how you could prepare two allotropic forms of one of them in the laboratory. How can it be proved that each form is the element in question and not another element or compound?

8. a) Describe a laboratory method for drying each of the following gases: ammonia, chlorine, carbon dioxide.

b) Describe the changes observed and give the formulas for the compounds formed when each of the following is exposed to the air of the laboratory: calcium oxide, nitric oxide, crystallized sodium carbonate, white lead. When the change is slow you may assume exposure for weeks if necessary. 9. Write in tabular form (a) the chemical name, (b) the formula, and (c) one important use for the following ten substances: calomel, lunar caustic, oil of vitriol, quartz sand, red lead, limestone, muriatic acid, blue vitriol, sal ammoniac, rouge.

10. a) A certain compound contains 25.0 per cent of carbon, 8.34 per cent of hydrogen, 66.66 per cent of sulphur. What is the simplest formula that can be written for it?

b) Calculate the percentage of potassium in carnallite (KCl MgCl2•6H2O). What weight of carnallite would be required to prepare one ton of potassium carbonate?

(Atomic weights: K 39, C1 35.5, S 32, Mg 24, O 16, C 12, H 1.)

11. a) Describe the electroplating of a spoon with silver, giving the composition of the bath and explaining the action which takes place in the solution and at each electrode.

b) How would you tell the positive from the negative electrode when passing a current through a water solution of sodium sulphate?

12. a) What weight and what volume of hydrogen may be represented by the formula H2? How do we know that it should be written H2 instead of H or H2?

b) What effect would a water solution of sodium carbonate have on litmus? How do you account for this? What is this phenomenon called?

13. a) Describe the metallurgy of zinc from its sulphide ore, using equations. b) Explain why a completely different method must be employed to obtain aluminum from its ore.

14. a) From what substances do (1) animals and (2) plants get the carbon, oxygen, and nitrogen they require for growth?

b) Draw a diagram of a furnace fire and indicate the chemical reactions taking place in different parts of it. Explain how this knowledge should be made use of in tending a fire.

15. a) Indicate the procedure by which river water can be tested for (1) soluble chlorides, (2) soluble carbonates, (3) soluble sulphates.

b) Could all of these ingredients be present and the water be "soft"? Explain your answer.

c) How can carbon dioxide be produced in preparing food without leaving a mineral residue?

d) Why is it not feasible to make soap from a mineral oil?

1925

Saturday, June 20

DRAWING-FREEHAND

Candidates must do all exercises.

2 p.m. Two hours.

An incomplete drawing, correctly laid out and executed by correct method, is better evidence of proficiency than a completed drawing incorrect in construction or slovenly in execution.

All work must be strictly freehand work without assistance from measuring slips, instruments, or artificial aids of any kind.

1. From the drawing shown in Figure 1 make a line sketch in perspective, showing the location of the horizon line and of all vanishing-points. Make the drawing (including the vanishing-points) as large as the paper permits. Do not put in any light and shade.