Answer to Question #120565 in General Chemistry for Ashley Arteaga

Question

A compound containing only Calcium and oxygen was mined in the Rocky Mountains. 39.95% of the compound is calcium. By mass there is four times as much Oxygen there is carbon. Find the empirical formula.

Answer 1

The sum of mass percents of Oxygen and Carbon is 100 - 39.95 = 60.05%.

Let x be the percentage of Carbon. Therefore, the percentage of Oxygen equals 4x.

x + 4x = 60.05;

x = 12.01

So the compound contains 12.01% of Carbon and 4 x 12.01 = 48.04% of Oxygen by mass.

Considering 100 g of the compound, there is 39.95 g of Ca, 12.01 g of C, and 48.04 g of O. To determine the empirical formula, the mole ratio of these elements should be calculated.

n (Ca) = 39.95g / 40.08g/mol ≈ 1 mol;

n (C) = 12.01g / 12.01g/mol = 1 mol;

n (O) = 48.04g / 16.00g/mol ≈ 3 mol.

Therefore the empirical formula is CaCO₃.

Answer: CaCO₃