ns in accordance with the equation

2C_{2}H_{2} + 5O_{2} = 4CO_{2} + 2H_{2}O.

Hence 2 volumes of acetylene will react with 5 volumes of oxygen to form
4 volumes of carbon dioxide and 2 volumes of steam. That the volume
relations may be correct a gaseous element must be given its molecular
formula. Thus oxygen must be written O_{2} and not 2O.

2. _Application to weights of gases._ It will be recalled that the
molecular weight of a gas is determined by ascertaining the weight of
22.4 l. of the gas. This weight in grams is called the _gram-molecular
weight_ of a gas. If the molecular weight of any gas is known, the
weight of a liter of the gas under standard conditions may be determined
by dividing its gram-molecular weight by 22.4. Thus the gram-molecular
weight of a hydrochloric acid gas is 36.458. A liter of the gas will
therefore weigh 36.458 / 22.4 = 1.627 g.

EXERCISES

1. From the following data calculate the atomic weight of sulphur. The
equivalent, as obtained by an analysis of sulphur dioxide, is 16.03. The
densities and compositions of a number of compounds containing sulphur
are as follows:

NAME DENSITY COMPOSITION BY PERCENTAGE
Hydrosulphuric acid 1.1791 S = 94.11 H = 5.89
Sulphur dioxide 2.222 S = 50.05 O = 49.95
Sulphur trioxide 2.74 S = 40.05 O = 59.95
Sulphur chloride 4.70 S = 47.48 Cl = 52.52
Sulphuryl chloride 4.64 S = 23.75 Cl = 52.53 O = 23.70
Carbon disulphide 2.68 S = 84.24 C = 15.76

2. Calculate the formulas for compounds of the following compositions:

MOLECULAR
WEIGHT
(1) S = 39.07% O = 58.49% H = 2.44% 81.0
(2) Ca = 29.40 S = 23.56 O = 47.04 136.2
(3) K = 38.67 N = 13.88 O = 47.45 101.2

3. The molecular weight of ammonia is 17.06; of sulphur dioxide is
64.06; of chlorine is 70.9. From the molecular weight calculate the
weight of 1 l. of each of these gases. Compare your results with the
table on the back cover of the book.

4. From the molecular weight of the same gases calculate the density of
each, referred to air as a standard.

5. A mixture of 50 cc. of carbon monoxide and 50 cc. of oxygen was
exploded in a eudiometer, (a) What gases remained in the tube after
the explosion? (b) What was the volume of each?

6. In what proportion must acet