Answer:
20 ounces of 14% solution and 8 ounces of 7% solution.
Explanation:
Let the amount of 14% solution required be A and the amount of 7% solution required be B.
Mixture of A and B must give 28 ounces:
A + B = 28 ................. Eqn 1
Also, mixture of 14% A and 7% B must give 12%, 28 ounces solution:
0.14A + 0.07B = 0.12(28) = 3.36...................Eqn 2
From eqn 1, B = 28 - A, eqn 2 becomes:
0.14A + 0.07(28 - A) = 3.36
0.07A = 3.36 - 1.96
A = 20 ounces
Substitute the value of A into eqn 1 to get B:
20 + B = 28
B = 8 ounces.
Hence, 20 ounces of 14% hydrochloric acid and 8 ounces of 7% hydrochoric acid should be mixed together in order to get 28 ounces of 12% solution.
