Question

0.5 g of an acid is neutralized by 40 cc of 0.125 N $NaOH$. The equivalent mass of the acid is

• A. 50
• B. 100
• C. 40
• D. 80

Answer 1

The correct option is B 100

40cc of 0.125 N NaOH corresponds to $\frac{\text{40 mL}}{\text{1000 mL/L}}\times \text{0.125 geq/L}=\text{0.005 g eq}$

0.005 g eq of $NaOH$ will neutralise 0.005 g eq of acid.

$\text{Equivalent mass of acid}=\frac{\text{mass}}{\text{number of gram equivalents}}$

$\text{Equivalent mass of acid}=\frac{\text{0.5 g}}{\text{0.005 g eq}}$

$\text{Equivalent mass of acid}=\text{100 g / eq}$
Hence, the equivalent mass of the acid is $100g/eq$.