Question

performing percent composition calculations
carbon dioxide (co₂) is a gaseous compound. calculate the percent composition of this compound. answer using one decimal place.
what is the percent by mass of carbon?
what is the percent by mass of oxygen?

Explanation:

Step1: Calculate molar mass of CO₂

The molar mass of C is 12.01 g/mol and O is 16.00 g/mol. For CO₂, molar mass $M = 12.01+2\times16.00=44.01$ g/mol.

Step2: Calculate percent by mass of carbon

Percent by mass of C $=\frac{12.01}{44.01}\times100\%\approx27.3\%$.

Step3: Calculate percent by mass of oxygen

Percent by mass of O $=\frac{2\times16.00}{44.01}\times100\%\approx72.7\%$.

Answer:

What is the percent by mass of carbon? 27.3%
What is the percent by mass of oxygen? 72.7%