The number of moles of CuO, that will be utilized in Dumas method for estimation nitrogen in a sample of 57.5g of N,

Moles of $\mathrm{N}$ in $\mathrm{N}, \mathrm{N}$ - dimethylaminopentane

$=\left(\frac{57.5}{115}\right)=0.5 \mathrm{~mol}$

$\Rightarrow \mathrm{C}_{7} \mathrm{H}_{17} \mathrm{~N}+\frac{45}{2} \mathrm{CuO} \rightarrow 7 \mathrm{CO}_{2}+\frac{17}{2} \mathrm{H}_{2} \mathrm{O}+\frac{1}{2} \mathrm{~N}_{2}+\frac{45}{2} \mathrm{Cu}$

$\frac{\mathrm{n}_{\mathrm{CuO}} \text { reacted }}{\left(\frac{45}{2}\right)}=\frac{\mathrm{n}_{\mathrm{C}_{7} \mathrm{H}_{17} \mathrm{~N}} \text { reacted }}{1}$

$\Rightarrow \mathrm{n}_{\mathrm{Cuo}}$ reacted $=\left(\frac{45}{2}\right) \times 0.5=11.25$