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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, H2SO4, AgNO3, NH, CI, Pb(NO3)2, Na,HPO4, CaCO3, (NH),50, and Cr,K,(S02) + 24H,0.

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

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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.

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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 ?

Describe experiments which show its lightness and rapid diffusion.

53. Sketch the apparatus you would use to demonstrate that hydrogen may be syphoned.

54. A burning jet of hydrogen is placed successively in air, in oxygen, in hydrogen, and in chlorine. State exactly what occurs in each case.

55. By what methods have Pictet and Cailletet liquefied hydrogen? Give a short account of previous unsuccessful attempts to effect this result.

56. The captive balloon at Paris in 1878 was 36 metres in diameter and spherical. What volume of gas at N.T.P. is required to fill it? What weight of hydrogen would be required ?

57. What impurities are generally found in hydrogen prepared by the action of acids on zinc, and how may they be completely removed ?

58. What impurity is always present in hydrogen which has been dried by passing the gas over strong sulphuric acid ? Explain its presence.

59. If you were provided with magnesium, sulphuric acid, water, and a graduated cylinder, how could you ascertain the combining weight of hydrogen ?

HYDROGENIUM (ALLOTROPIC HYDROGEN).

60. Give a short account of the substance called by Graham “hydrogenium,” and state how it is prepared.

61. Explain the terms “occlusion,” “diffusion,” “ effusion,” and “transpiration ” of gases.

Give examples of each.

62. How has the density of hydrogenium been ascertained ? In what respects does hydrogenium resemble a metal ?

63. Contrast the chemical properties of hydrogen with those of hydrogenium.

64. Give an example of a reaction in which hydrogen acts like a metal. What property, characteristic of metals and their compounds, is possessed by hydrogenium ?

a

CHLORINE.

65. By whom and in what year was chlorine gas discovered ? By whom and when was it shown to be an eleinent ?

66. Name several commonly occurring compounds which contain chlorine.

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