Two solutions of different concentrations of acid are mixed creating 40 mL of a solution that is 32 percent acid. One-quarter of the solution is made up of a 20 percent acid solution. The remaining three-quarters is made up of a solution of unknown concentration, c Which equation can be used to determine c , the unknown concentration?
Answer
A
3 fourths c open paren 1 fourth times 0 point 2 close paren is equal to 40 times 0 point 3 2
B
30 c open paren 10 times 0 point 2 close paren is equal to 40 times 0 point 3 2
C
30 c plus 10 times 0 point 2 is equal to 40 times 0 point 3 2
D
3 fourths times c plus 1 fourth times 0 point 2 is equal to 40 times 0 point 3 2
Explanation
One-quarter of 40 mL is 10 mL, so the 20% solution contributes 10 × 0.2 mL of acid. The remaining 30 mL contributes 30c mL of acid. The mixture contains 40 × 0.32 mL of acid in total, so the equation is 30c + 10 × 0.2 = 40 × 0.32, which is choice C.
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