Establish and write down the formula of carbon monoxide if it is known that it belongs

Establish and write down the formula of carbon monoxide if it is known that it belongs to oxides and the mass fraction of carbon in it is 42.86 percent.

Given:
CxOy
ω (C in CxOy) = 42.86%

Find:
CxOy -?

Solution:
1) Let m (CxOy) = 100 g;
2) m (C in CxOy) = ω (C in CxOy) * m (CxOy) / 100% = 42.86% * 100/100% = 42.86 g;
3) n (C in CxOy) = m (C in CxOy) / M (C) = 42.86 / 12 = 3.572 mol;
4) m (O in CxOy) = m (CxOy) – m (O in CxOy) = 100 – 42.86 = 57.14 g;
5) n (O in CxOy) = m (O in CxOy) / M (O) = 57.14 / 16 = 3.571 mol;
6) x: y = n (C in CxOy): n (O in CxOy) = 3.572: 3.571 = 1: 1;
The formula for carbon monoxide is CO.

Answer: The formula for carbon monoxide is CO.