Question

WHAT IS THE PERCENTAGE COMPOSITION OF OXYGEN IN EACH OF THE FOLLOWING SUBSTANCES:
1)CO
2) Calcium nitrate

Answer 1

Molar mass of CO = 12 + 16
= 28 g mol^-1
Molar mass of Calcium nitrate, Ca(NO₃)₂ = 40 + 2(14 + 48)
= 164 g mol^-1
$$\begin{gathered} \text{\% composition of an element}=\frac{\text{Mass of an element in compound}}{\text{Total mass of compound}}\times 100 \\ \text{Mass of Oxygen in CO = 16 g} \\ \text{Mass of Oxygen in Calcium nitrate}=2(3\times 16) \\ \text{= 96 g} \\ \text{\%composition of oxygen in CO}=\frac{16}{28}\times 100 \\ =57.14 \\ {\text{\%composition of oxygen in Ca(NO}}_{\text{3}}{\text{)}}_{\text{2}}=\frac{96}{164}\times 100 \\ =58.54 \end{gathered}$$