Question

If 20 ml of 0.4 M NaOH solution is completely neutralised by 40ml of a dibasic acid, the molarity of the acid solution is :

• A. $0.1M$
• B. $0.2M$
• C. $0.3M$
• D. $0.4M$

Answer 1

Answer: (A)

$0.1M$

For neutralization, no. of equivalent should be same,

$N_1{V}_1=N_2{V}_2$

$0.4\times 20=N_2\times 40$

$N_2=\frac{0.4\times 20}{40}$

$N_2=0.2N$

Also we know that $M=\frac{N}{n}$

where n is n-factor of acid.

n-factor of acid will be 2, because it is dibasic acid

Therefore,

$M_2=\frac{N_2}{2}$

$M_2=\frac{0.2}{2}$

$=0.1M$

Thus molarity of the acid solution is $0.1M$.

Thus, the correct option is A.