The graph shows the solubility of several different salts in water, across a range of temperatures. According to the
graph, which salt can dissolve at a concentration of about 60 g/100 cm3 of water at 40 degrees Celsius?

A) sodium nitrate
B) sodium chloride
C) potassium iodide
D) potassium nitrate

Explanation:

The attached graph with a green and a red arrow facilitates the understanding of this explanation.

To read the solubility on the graph, you can start with the temperature, on the x-axis.

The red vertical arrow shows how, departing from the 40ºC temperature on the x-axis, you intersect the solutibility curve of sodium chloride at a height (y-axis) corresponding to 60 g/100cm³ of water (follow the green horizontal arrow).

Hence, sodium chloride is the salt that can dissolve at a concentration of about 60g/100cm³ of water at 40ºC.

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%