Question

If a copper-containing compound contains $4.999$% $Cu$ by mass and there are $2$ copper atoms per formula unit, what is the molar mass of the compound?

• A. $2547g/mol$
• B. $47.50g/mol$
• C. $31.75g/mol$
• D. $1274g/mol$

Answer 1

The correct option is A $2547g/mol$

Let molar mass of compound $=M$

In $1mole$ of compound there are two Copper atoms i.e. $128gms$ of Copper.

Given, $4.999\%$ ofCopper by mass

So, $\left(\%\text{of Copper}\right)\times \text{Molar mass}=\text{Mass of Copper}$

$\Rightarrow \left(\frac{4.999}{100}\right)\times M=128gms$

$\Rightarrow M=\frac{12800}{4.99}=2547g/mol$