Question

If we have a pure $Ca(N{O}_3{)}_2$ sample that contains a total of 1.64 kilomoles of electrons then find the number of moles of $Ca(N{O}_3{)}_2$ present in the sample.

• A. 10 moles
• B. 20 moles
• C. 30 moles
• D. 40 moles

Answer 1

The correct option is B 20 moles

One molecule of $Ca(N{O}_3{)}_2$ contains $=20+(2\times 7)+(6\times 8)=82$ electrons.
So, number of electrons in 1 mole of $Ca(N{O}_3{)}_2=82\times 6.022\times {10}^{23}$.
Therefore, 1.64 kilomoles of electrons will be present in
$=\frac{1.64\times 1000\times 6.022\times {10}^{23}}{82\times 6.022\times {10}^{23}}$ moles of $Ca(N{O}_3{)}_2$
$=$ 20 moles of $Ca(N{O}_3{)}_2$