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

Answer: (A)

75%

Number of moles of $Cu$ in $66.6g=\frac{66.6g}{63.5}=1.05$ moles

We have $1$ mole of oxygen per $2$ mole of $Cu$

So, moles of oxygen is $0.525$.

Weight of oxygen present= $0.525mol\times 16g/mol=8.4g$

So, we have $(66.6+8.4)g=75g$

Our sample is $75$% pure $C{u}_{2}O$.