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QUESTIONS ON CHEMISTRY.

SECTION 1.-NON-METALS.

INTRODUCTORY SUBJECTS.

1. WHAT is meant (a) by chemical action, (6) by physical change ?

2. Give some familiar examples of chemical action and physical change.

3. Explain the terms chemical combination and chemical decomposition. Give examples.

4. Matter is said to be indestructible. Explain this statement, and describe an experiment in support of it.

5. The following substances are heated to redness in air-(a) platinum, (6) magnesium, (c) mercuric oxide. What occurs in each case ?

6. Some finely divided copper is placed in an open crucible and its weight ascertained. It is then heated to redness, allowed to cool, and when re-weighed is found to have gained in weight. How is this accounted for?

7. Name the elements contained in an ordinary candle, and explain fully the chemical changes which occur when it burns in air.

8. When the products from the burning of a candle are collected and weighed, do they weigh more or less than the original candle ? What is the cause of the difference in weight ?

9. What is the difference between elements and compounds ? Give six examples of each.

10. Into what two classes are elements divided, and how many are in each class ?.

11. Make a sketch of a chemical balance and explain its construction. Who first introduced the use of the balance in chemical investigations ?

12. How would you endeavour to ascertain whether a certain substance was an element or a compound?

13. Name the most abundant elements (a) in the earth, (6) in the air.

14. What is meant by each of the following terms

(a) chemical test, (6) analysis, (c) synthesis ? Give examples of each.

15. Distinguish the elements from the compounds in the following list of substances :-sand, sugar, ozone, phosphorus, glass, water, lime, chlorine, chalk, nitre, diamond, mercury, common salt, silver and potassium chlorate.

16. Name the non-metallic elements, and state which are most abundant in nature.

17. Each element has a certain symbol, combining weight, and density. Explain these terms.

18. What is the weight in grammes of a litre of hydrogen at the normal temperature and pressure? (i.e. at a temperature of o° C. and under a pressure of 760 millimetres of mercury=N.T.P.).' Why is it important to remember this weight and what name has been given to it?

19. Give the weight in grammes at N.T.P. of a litre of each of the following gases-oxygen, chlorine, nitrogen, carbon dioxide and hydrochloric acid.

1 It is convenient to indicate these conditions by a shorter expression. Here and elsewhere in the book “normal temperature and pressure contracted thus, N.T.P.

is

20. A certain volume of oxygen weighs i gramme. Find the weights at the same temperature and pressure of the same volume of carbon dioxide, nitrogen, chlorine, ammonia, and hydrochloric acid.

21. How are the French measures of weight and capacity derived from the measures of length ?

22. How many grains are in a gramme, how many inches in a metre, and how many cubic centimetres in a litre ?

23. Find the dimensions of a room in metres which is 24 feet long by 15 broad and 13 high.

24. A sample of water contains 2'23 grammes of solid matter in a litre. How many grains per gallon does this correspond to ?

25. State shortly the laws enunciated by Dalton and by Gay Lussac on the subject of chemical combination.

26. Chemical combination is said to take place in certain definite proportions. Explain this and give an example.

27. One hundred pounds of copper are heated with the same weight of sulphur till combination takes place. Which element would be found in excess after the reaction, and how much of it?

28. 63.5 grammes of copper, 207 grammes of lead, and 24 grammes of magnesium are separately heated in air till they cease to gain in weight. How many grammes will each gain?

29. A solution contains 159'5 grammes copper sulphate. How much iron is required to precipitate all the copper, and what weight of ferrous sulphate is formed ?

30. In what proportions (a) by weight, (6) by volume, do oxygen and hydrogen unite together? Answer the question also for hydrogen and chlorine.

31. Find the volumes at N.T.P. of 1 gramme hydrogen, 16 grammes oxygen, 14 grammes nitrogen, 35'5 grammes chlorine, 80 grammes bromine vapour, 9 grammes water vapour, 18-25 grammes hydrochloric acid, and 22 grammes carbon dioxide.

32. Name the elements represented by the following symbols :-C, CI, Cu, Ca, Cd, Co, S, Si, Sr, Mg, Mn, K, Ag, Hg, Sb, Pb, and Na.

33. Express the following equations in words :-

8

H + Ci HCI.
H, + 0 H20.
Cu + S

CuS.
P, +03 = P205.

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