Question

Two acids $H_2{SO}_4$ and $H_3{PO}_4$ are neutralized separately by the same amount of an alkali when sulphate and dihydrogen orthophosphate are formed, respectively. Find the ratio of the masses of $H_2{SO}_4$ and $H_3{PO}_4$ :

• A. $1:1$
• B. $1:2$
• C. $2:1$
• D. $2:3$

Answer 1

The correct option is B $1:2$

$H_2{SO}_4+2NaOH\to {Na}_{2}S{O}_4+2H_{2}O$

$H_{3}P{O}_4+NaOH\to {NaH}_2{PO}_4+H_{2}O$

Equivalent of alkali= 1 g equivalent of $H_2{SO}_4$ =1 g equivalent of $H_{3}P{O}_4$

The two acids must react in the ratio of their equivalent masses.

Equivalent mass of $H_2{SO}_4$ = $\frac{98}{2}=49$

Equivalent mass of $H_{3}P{O}_4$ $=\frac{98}{1}=98$

Hence ratio of masses of $H_2{SO}_4$: $H_{3}P{O}_4$ =$49:98=1:2$