40 QUANTITATIVE ASPECTS OF CHEMISTRY
- The oxide formed when 1 gram of sulphur is burned
weighs exactly 2 grams. What is the combining ratio by
weight of sulphur and oxygen? - Using the data and assumptions of the last two prob-
lems and the atomic weight of oxygen as 16, deduce the atomic
ratio by which sulphur and oxygen combine. Write the for-
mula of this compound. - From the atomic weights printed in the table, find the
percentage composition by weight in the compounds having
the atomic ratio expressed by the formulas CaO, Li 2 O, Fe2O 3 ,
Fe-A. - One oxide of chromium contains 52 per cent of chro-
mium and 48 per cent of oxygen by weight; another contains
68.42 per cent of chromium and 31.58 per cent of oxygen.
Prove that these compounds are in agreement with the law
of multiple proportions. - Look up the atomic weight of chromium and find the
atomic ratio in each oxide. Write the simplest formula of
each oxide. - One gram of potassium metal burns to give 1.82
grams of an oxide. Calculate the chemical formula of the
oxide. - The oxide obtained when iron is burned in oxygen has
the composition Fe = 72.4; 0 = 27.6. Calculate the chem-
ical formula of the oxide. - Find the formula of the substance whose composition
is magnesium 25.57 per cent, chlorine 74.43 per cent. - Find the formula of the substance whose composition
is potassium 26.585, chromium 35.390, oxygen 38.025.
Measurement of Gases. Since it is difficult to weigh a body
of gas, but comparatively easy to find its volume, the amounts of
gases are almost invariably estimated by measuring the volume.
But the volume of a definite amount of gas is very dependent on
the conditions, and to make a volume measurement have an
accurate meaning it becomes necessary to know exactly the
conditions of pressure, temperature, and dryness under which
the measurement is made. To make the results of all measure-
ments comparable it is customary to calculate what the measured
volume would become if so-called standard conditions prevailed.