How much water must be added to 100 cc of a 60% solution of sulphuric acid to reduce it to a 40% solution?
- 20 cc
- 30 cc
- 40 cc
- 50 cc
- 60 cc
The Usual Method
Let ‘x’ cc be the amount of water added to 100 cc of sulphuric acid. Concentration of acid in water = 0%
Estimated Time to arrive at the answer = 45 seconds.
In order to reduce concentration from 60 to 40 (i.e. by 33.33%) we need to increase the quantity of the solution by 50% (See concept explained in section of Percentages in Stuff to Remember.)
Thus if solution initially was 100 cc, it should now be 150 cc. Thus additional 50 cc is to be added.
Estimated Time to arrive at the answer = 10 seconds.