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20. A certain volume of oxygen weighs 1 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 :-

H + Cl = HCI.
H + 0 = H,O.
Cu + S

CuS.
P, +0= P,0%

34. Give the combining weight of each element, and the molecular weight of each compound mentioned in the previous question.

35. Find the molecular weights of the compounds represented by the following formulæ :-CuSO4, HNO3, H,SO,, AgNO3, NH,CI, Pb(NO3)2, Na2HPO4, CaCO3, (NH4)2SO4 and Cr,K2(SO4)4 + 24H,0.

36. Give the formulæ for hydrochloric acid and for the chlorides of,

Sodium, potassium, and silver (monads) ;
Calcium, zinc, lead, and barium (dyads); and for
Gold and boron

(triads).

37. Give the formulæ for nitric and sulphuric acids, and for the nitrates and sulphates of potassium, silver, calciuin, and lead.

MONADS.

HYDROGEN.

38. How is hydrogen found in the free state in nature ? How does it occur in combination ?

39. How long has hydrogen been known ? Who first obtained it pure and described its properties ?

40. Give three distinct reactions by means of which hydrogen may be obtained from water. Give equations for each reaction.

41. How is hydrogen usually prepared, and what impurities may it contain when prepared by this method ?

42. What occurs when zinc is heated with a strong solution of caustic potash or soda ? Give an equation.

43. How could you obtain hydrogen from (a) hydrochloric acid gas, (6) ammonia gas, (c) marsh gas ?

44. Name any four metals which if dropped into hydrochloric or sulphuric acids decompose these acids with evolution of hydrogen. Give equations.

45. Equal weights of potassium, lithium, and sodium, are placed in contact with water, and the hydrogen produced by each reaction is collected separately. Which metal will yield the greatest volume, and why?

46. What weight of hydrogen should be evolved by throwing II'5 grammes of sodium on water, and what volume should it occupy at N.T.P. ?

47. How much zinc must be dissolved in acid so as to yield exactly one litre of hydrogen at N.T.P. ?

48. Two hundred and fifty c.c. of hydrogen were obtained by dissolving iron in hydrochloric acid. How much of the metal was used ?

49. A gas-holder has the capacity of i cubic metre. Find the weight of zinc and sulphuric acid which must be used to fill it with hydrogen measured at N.T.P. ?

50. One hundred and twentry-three grammes of magnetic iron oxide remained in a tube in which iron had been heated in a current of steam. How much hydrogen was obtained, and what weight of iron oxidized ?

51. Two hundred and seventy-six grammes of potassium are thrown on water. Give the volume of gas. liberated and the weight of potash formed.

52. What are the chief properties of hydrogen?

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