what is the percentage by mass of oxygen (o) in a formula unit of potassium hydrogen carbonate (khco₃)?\na…

Explanation:

Step1: Calculate molar - mass of $KHCO_3$

The molar masses of $K = 39.1\ g/mol$, $H=1.01\ g/mol$, $C = 12.01\ g/mol$, $O = 16.00\ g/mol$. $M_{KHCO_3}=39.1 + 1.01+12.01 + 3\times16.00=39.1+1.01 + 12.01+48.00 = 100.12\ g/mol$

Step2: Calculate total mass of oxygen in $KHCO_3$

There are 3 oxygen atoms in $KHCO_3$. The total mass of oxygen, $m_O=3\times16.00 = 48.00\ g/mol$

Step3: Calculate mass - percentage of oxygen

The mass - percentage of oxygen, $\text{Mass}%=\frac{m_O}{M_{KHCO_3}}\times100%=\frac{48.00}{100.12}\times100%\approx47.95%$

Answer:

B. 47.95%