Question

A student weighed out a 2.055 g sample of a cobalt chloride hydrate, ConClmpH2O, where n, m, and p are integer values to be determined. The student heated the sample to drive off the waters of hydration, reweighed the anhydride sample and found 1.121 g anhydrate

Answer 1

The given mass of cobalt chloride hydrate = 2.055 g

A sample of cobalt chloride hydrate was heated to drive off waters of hydration and the anhydrate was weighed.

The mass of anhydrous cobalt chloride = 1.121 g anhydrate.

The mass of water lost during heating = 2.055 g - 1.121 g = 0.934 g

Converting mass of water of hydration present in the hydrate to moles using molar mass:

Mass of water = 0.934 g

Molar mass of water = 18.0 g/mol

Moles of water = $0.934 g * \frac{1 molH_{2}O }{18 g H_{2}O } =0.0519 mol H_{2}O$