Question

Substance Y is an oxocarbon, composed of carbon and oxygen. Mass data was collected showing that $0.39g$ of carbon atoms react with $1.00g$ of oxygen atoms to form substance Y.
What is substance Y?

• A. Carbon monoxide.
• B. Carbon dioxide.
• C. Carbonate ion.
• D. Tircarbon dioxide.

Answer 1

Answer: (B)

Carbon dioxide.

Carbon is 12 g/mol and oxygen is 16 g/mol.

To help with mental math, round and convert numbers to scientific notation:

$4\times {10}^{-1}$ g C and $1\times 100$ g $O$.

Divide by molar masses = $\frac{4\times {10}^{-1}gC}{12g}$ = $0.333\times {10}^{-1}$ = $0.0333$

and

$\frac{1\times 100}{16}$ = 0.0625.

There is about double the amount of oxygen by mass in the compound. Carbon dioxide is $C{O}_2$ and best fits the data.

B is answer