A 100.-mL sample of water is taken from the Pacific Ocean, and the water is allowed to evaporate. The salts that remain (mostly NaCl) have a mass of 3.85 g. Calculate the original concentration of NaCl, in g per liter, in the water sample.
A) 32.5 g/L
B) 34.5 g/L
C) 36.5 g/L
D) 38.5 g/L
E) None of the above

Question

Quizplus · Accepted Answer

The mass of the salts (mostly NaCl) remaining after evaporation is 3.85 g. Since NaCl is the most abundant salt in seawater, we assume all of the remaining salts to be NaCl.

To calculate the original concentration of NaCl in the water sample, we use the formula:

Concentration = (mass of solute) / (volume of solution)

We know the volume of the solution is 100 mL, or 0.1 L. The mass of solute is 3.85 g. So,

Concentration = 3.85 g / 0.1 L = 38.5 g/L

Therefore, the original concentration of NaCl in the water sample is 38.5 g/L. The correct answer is D.

A 100-ML Sample of Water Is Taken from the Pacific Ocean