Question

Describe how the molarity changes if you dissolve 10.0 g of NaCl in increasingly larger volumes of water.

a) The molarity decreases.
b) The molarity increases.
c) The molarity remains constant.
d) The molarity becomes zero.

Answer 1

The molarity decreases when 10.0 g of NaCl is dissolved in increasingly larger volumes of water, because the constant mass of solute is dispersed in a greater volume of solvent.

Step-by-step explanation:

When 10.0 g of NaCl is dissolved in increasingly larger volumes of water, the molarity of the solution changes in the following way: it decreases. Molarity is defined as the number of moles of solute (in this case NaCl) per liter of solution. As the amount of NaCl is constant (10.0 g), when it is dissolved in larger volumes of water, the concentration of NaCl per liter, which is molarity, decreases because the same amount of solute now spreads over a greater volume.

In other words, if we dissolve the NaCl in a larger volume of water, each liter of that solution has fewer moles of NaCl compared to when it was dissolved in a smaller volume. To calculate molarity, you would need the volume of the solution (in liters) and the number of moles of NaCl. Since the mass of NaCl is constant and only the volume of water changes, the molarity will be inversely proportional to the volume increase.