You have 100.0 mL of a 0.2500 M solution of NaCl sitting in a beaker. After several days you test the solution and find that it is now 0.3125 M. How much water must have evaporated?
Group of answer choices
20.0 mL
80.0 mL
10.0 mL
The concentration will not change because of evaporation.
90.0 mL
To find out how much water must have evaporated, we need to understand that the amount of solute (NaCl) remains constant during evaporation.
Using the formula for molarity (M1V1 = M2V2), we can set up the equation as follows:
(0.2500 M)(100.0 mL) = (0.3125 M)(V2)
Solving for V2, we get:
V2 = (0.2500 M)(100.0 mL) / (0.3125 M)
V2 = 80.0 mL
Therefore, 80.0 mL of water must have evaporated.
The correct answer is 80.0 mL.