Question

You have two distinct gaseous compounds made from element X and element Y. The mass percents are as follows:

Compound I: 26.97% X, 73.03% Y

Compound II: 59.63% X, 40.37% Y

In their natural standard states, element X and element Y exist as gases. (Monatomic? Diatomic? Triatomic? That is for you to determine.) When you react "gas X" with "gas Y" to make the products, you get the following data (all at the same pressure and temperature):

1 volume "gas X" + 2 volumes "gas Y" → 2 volumes compound I

2 volumes "gas X" + 1 volume "gas Y" → 2 volumes compound II

Assume the simplest possible formulas for reactants and products in these chemical equations. Then determine the relative atomic masses of element X and element Y.

Atomic mass Y =

Atomic mass X 1

Answer 1

Given mass percent of elements, assume 100g of each compound.

Thus, Compound I : 26.97g X and 73.03g Y

Compound II : 59.63g X and 40.37g Y

From the given information, we can write following two equations:

X + 2Y 2 (compound I)

2X + Y 2 (compound II)

As we have assumed 100g of the compounds, we can write

X + 2Y 2 (26.97g X + 73.03g Y)

2X + Y 2 (59.63g X + 40.37g Y)

Add these two equations, we get

3X + 3Y 173.2g X + 226.8g Y

divide the equation by 3

X + Y 57.73g X + 75.6g Y

Hence, relative mass of X = 57.73 g and Y = 75.6 g