Question

you are given an unknown gaseous binary compound. when 10.0g of the compound isburned in excess oxygen, 16.3g of water is produced. the compound has 1.38 times that of oxygen gas at the same conditions of temperature and pressure. give a possible identity for the compound.

Answer 1

Since the compound has 1.38 time that of oxygen gas at the same conditions of temperature and pressure, we have the relationship:
MW/MWoxygen = 1.38
MW = 44.16

Since there is water formed during the reaction, the formula of the compound must be:
XaHb
where a and b are the coefficients of each element.

If the compound reactions with oxygen forming water and an oxide of the element X, the combustion reaction must be:
XaHb + ((2a + (b/2))/2) O2 = a (XO2) + (b/2)(H2O)
Using dimensional analysis:
10 (1/44.16) (b/2 / 1) (18) = 16.3
Solving for b:
b = 8

The compound now is XaH8. Most probably, the compound is C3H8 since it has a molecular formula of 44 and it reacts with O2 to form water and CO2.