Question

A sample of impure cuprite, $C{u}_{2}O$, contains 66.6% copper. What is the percentage of pure $C{u}_{2}O$ in the sample?

• A. 75%
• B. 25%
• C. 60%
• D. 80%

Answer 1

The correct option is A 75%

66.66% of copper in $100\text{g}$ is $66.66\text{g}$ of copper.
If we take pure $C{u}_{2}O$
$2\times 63.5\text{g}$ of $Cu$ is present in $143\text{g}$ of the compound.
$100\text{g}$ of the compound contains = $\frac{100}{143}\times 2\times 63.5=88.8\text{g of}Cu$
Percentage purity = $\frac{66.66}{88.8}\times 100=75\%$