Question

16. To make a 100 litre solution of acid 40% from 50%. How
much water must added ?
(1) 50 litre
(2) 75 litre (3) 15 litre
(4) 10 litre
(5) 25 litre​

Answer 1

Answer:

Let Ma = Mw = 50 l

Ma / (100 + x) = .4        where x is the water added

(Mw  + x) / (100 + x) = .6       the solution is now 60% water

Mw + x  / Ma = 1.5       dividing the second equation by the first

Mw + x = 1.5 Ma

x = 1.5 Ma - Mw = 1.5 * 50 - 50 = 25   since Mw = Ma = 50

So 25 liters of water must be added

Check:    50 / 125 = .4    and 75 / 125 = .5

This is assuming that you started with 100 liters - The problem does

not make this very clear