A stream of aqueous sulphuric acid of 62.4 wt% H2SO4 is mixed with pure water in a stirred vessel to produce a stream of 20.5 wt% acid. What ratio of water to concentrated acid should be used?
62.4 - 20.5 = 21.9 ml
0 - 20.5 = 20.5 ml
To get 20.5 wt% solution we need 21.9 ml of 62.4 wt% H2SO4 solution and 20.5 ml of H2O.