Question

How much water should be added to 200 cc of a seminormal solution of NaOH to make it exactly decinormal:

• A. 1000 cc
• B. 400 cc
• C. 800 cc
• D. 600 cc

Answer 1

Answer: (C)

800 cc

Given that:

Initial volume of the solution, $V_1=200c{m}^3$

Initial normality of solution, $N_1=\frac{1}{2}N$

Final normality of solution, $N_2=\frac{1}{10}N$

Now,

By law of equivalence-

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

$V_2=\frac{N_1{V}_1}{N_2}=\frac{\frac{1}{2}N\times 200c{m}^3}{\frac{1}{10}N}$

$=1000c{m}^3$

$\therefore$ Volume of water added, $V=V_2-V_1$

$=(1000-200)c{m}^3=800c{m}^3$