Question

A $5.0g$ sample of copper(II) oxide containing an inert contaminant is analyzed and found to contain $3.0gCu$. Using molar masses of $64g/mol$ for copper, and $16g/mol$ for oxygen, determine the percent purity of the copper(II) oxide sample.

• A. $80$%
• B. $75$%
• C. $60$%
• D. $50$%

Answer 1

The correct option is B $75$%

Given, Mass of $CuO$ sample $=5g$

Mass of $Cu$ found $=3g=\frac{3}{64}moles$ of Copper

So, $\frac{3}{64}moles$ of $CuO$ must be present

Mass of $\frac{3}{64}moles$ of $CuO=\frac{3}{64}[64+16]=3.75g$

So, percentage of Purity$=\frac{3.75}{5}\times 100=75\%$