You have 40g of sodium chloride. What is the minimum amount of water required to dissolve the salt at 30oC?

Jun 18, 2018

The minimum mass of water is 111 g.

Explanation:

Step 1. Determine the solubility of $\text{NaCl}$ at 30 °C

I am guessing that "they" are asking you to get the information from a solubility curve for sodium chloride like the one below.

From 30 °C on the horizontal axis, draw a vertical line up until it hits the solubility curve (blue) for $\text{NaCl}$.
The solubility is $\text{36 g NaCl/100 g water}$.
$\text{Mass of water" = 40 color(red)(cancel(color(black)("g NaCl"))) × "100 g water"/(36 color(red)(cancel(color(black)("g NaCl")))) = "111 g water}$