ON TEACHING CHEMISTRY. 275 
7. The following formule are given tv acetic acid : (a) C,H,0,, (L) CH,.COOH : 
indicate some of the advantages of the second formula as compared with the 
first. 
InorGanic CHEMISTRY, 
1, Explain briefly the meaning of the following chemical symbols and 
equations : 
0; 0,; 2KC1O, =2KC1+30,; 2H, +0, =2H,0. 
2. Describe, as fully as you can, one instance of a chemical change, and one of 
a physical change; and point out the chief differences between them. 
5. With 1 part by weight of hydrogen there combine 16 parts by weight of 
sulphur; with 8 parts by weight of oxygen there combine, in one case 8 parts by 
weight of sulphur, and in another case 5°33 parts by weight of sulphur. State in 
general terms how you would determine whether 5°33, 8, 16, or a common mul- 
tiple of these numbers, would be the best combining weight to use for sulphur. 
4, What do you understand by the chemical properties of an element? Illus- 
trate your answer by describing what you regard as the chief chemical pro- 
perties of any one of the following elements: chlorine, sulphur, magnesium, iron, 
chromium. 
5. The compounds KOH and NaOH are called alkalis: why are these com- 
pounds classed together under a common name, and what is the chemical meaning 
of the term alkali ? 
6. You are given an aqueous solution of two salts, one of which is muck 
more soluble than the other: how would you proceed to effect a partial separation 
of the salts ? 
7. Sugar is composed of the three elements carbon, hydrogen, and oxygen: 
how can this statement be proved? Why are the substances carbon, hydroger., 
and oxygen called elements ? 
Practica Work. 
Write out a clear and full description of all your experiments ; state very carefully 
and fully the reasoning on each result obtained. 
[Not more than Two questions to be attempted. ]} 
[ Time allowed, 3 hours. | 
1. Determine, as far as you can by qualitative experiments, whether the sub- 
stance A is a mixture of two salts or a double salt. 
2. To B add a solution of bleaching-powder, and heat to boiling; to C add 
dilute sulphuric acid; from the results observed identify B and C as far as 
you can. 
5. The substance D is either an acid, a base, or a salt: find which it is. 
LOWER CERTIFICATES. 
CHEMISTRY. 
I, 
1. Explain why water is regarded as a compound, and air as a mixture. 
_ 2. How may hydrogen be liberated from water? If you wished to obtain 44:8 
litres of hydrogen by dissolving iron or zinc in acid, what weight of each should 
_beused? [Fe = 56, Zn = 65, 11-2 litres of hydrogen weigh one gramme. | 
3. How is hydrochloric acid obtained ? For what reasons is it called an acid ? 
How are metallic salts formed from it? Give examples. 
4. Describe briefly and explain what changes take place in the following 
reactions : (a) potassium nitrate with strong sulphuric acid ; (4) diluted nitric acid 
with copper; (c) strong nitric acid with phosphorus; (d@) ammonium nitrate if 
exposed to heat. 
_5. What oxides are formed when sulphur and phosphorus burn, and what 
acids are formed by the union of the oxides with water ? 
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