Question

Calculate the number of oxalic acid molecules in $100mL$ of $0.02N$ oxalic acid.

• A. $6.023\times {10}^{20}$
• B. $6.023\times {10}^{21}$
• C. $6.023\times {10}^{22}$
• D. $6.023\times {10}^{23}$

Answer 1

The correct option is A $6.023\times {10}^{20}$

Normality = Molarity $\times$ Valence factor
$\therefore$ Molarity $=\frac{\text{Normality}}{\text{Valence factor}}$
$\text{Valence factor for oxalic acid}=\frac{\text{Molecular weight of oxalic acid}}{\text{Equivalent weight of oxalic acid}}=\frac{126}{63}=2$
Molarity $=\frac{0.02}{2}=0.01$

$\text{Number of millimoles}=0.01\times 100=1$
$\therefore \text{Number of moles}=0.001$
$\text{Number of oxalic acid molecules}=0.001\times 6.023\times {10}^{23}=6.023\times {10}^{20}$