Question

62. A chemist mixes 15 liters of 40 percent acid solution and 25 liters of 20 percent acid solution.

What percent of the mixture is acid?

Answer 1

40% of 15 L = 6 L of acid

20% of 25 L = 5 L of acid

This means the mixture contains a total of 11 L of acid, and with a total volume of 15 L + 25 L = 40 L, that means the mixture is at a concentration of

(11 L acid) / (40 L solution) = 0.275 = 27.5%