A 19.79g sample of hydrated CoCl² weighs 10.77g after being heated. Determine the formula of the compound. Show all of your work and write your final answer below. (Hint: Start by finding the moles of CoCl² and the moles oh H²O)

Given that it is a hydrate, the formula will look like this, CoCl₂ · x H₂O

our job is to figure out how many molecules of water (H₂O) there are in the compound, this is the x value.

1) first, we figure out the weight of water. we already have the weigh of CoCl₂, which is 10.77 grams. the fact that after heating, the sample weighs less means that the water was evaporated. in order to find the weight of water, we just subtract the amount with water and after the water lost.

mass of water = 19.79 - 10.77 = 9.02 grams

2) let's now convert each gram of compound CoCl₂ and H₂O to moles using their molar masses. remember that you just need to add the mass of each atom in the compound from the periodic table to get the molar mass.

molar mass of CoCl₂ = 58.9 + (2 x 35.5) = 129.9 g/mol

molar mass of H₂O = 16.0 + (2 x 1.01) = 18.0 g/mol

10.77 g (1 mol / 129.9 g) = 0.0829 mol CoCl₂

9.02 g (1 mol / 18.0 g) = 0.501 mol H₂O

3) to find the water ration, let's take the moles of water over the moles of the CoCl₂.

0.501 / 0.0829 = 6.0

we found X!

the answer is CoCl₂ · 6 H₂O