You have 120.0 mL of a 0.275 M solution of NaCl sitting in a beaker. After several days you test the solution and find that it has a concentration of 0.356 M. How much water must have evaporated? (Assume volumes are additive.)
A) 92.7 mL
B) 27.3 mL
C) 120 mL
D) 213 mL
E) 119 mL

Question

Quizplus · Accepted Answer

The concentration of a solution can be calculated using the formula:

C1V1 = C2V2

where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume.

In this case, we know that:

C1 = 0.275 M
V1 = 120.0 mL
C2 = 0.356 M
V2 = ?

We can rearrange the formula to solve for V2:

V2 = (C1V1) / C2

V2 = (0.275 M x 120.0 mL) / 0.356 M

V2 = 92.7 mL

So the final volume of the solution is 92.7 mL. Since the initial volume was 120.0 mL, there must have been 27.3 mL of water that evaporated. Therefore, the answer is B.

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