Question

A hydrate of Cobalt(ii)Chloride had mass of 166.04g before heating. After heating, the anhydrous CoCl₂ weighed 130.9g.

- what is the mass of the water that was driven off?

- how many moles of water were driven off?

- how many moles of anhydrous CoCl₂ remain?

- what is the hydration number (moles of water per mole compound)?

Answer 1

Answer 2

From the given information -

a) The mass of water driven off from the salt = 166.04 g - 130.9 g = 35.14 g

b) The number of mols of water = 35.14 g / 18 g/mol = 1.952 mol

c) Since, there are 130.9 g of CoCl₂ after dehydration, the number of mols of CoCl₂

                                                      = 130.9 g /129.84 g/mol = 1.008 mol

d) The hydration number 1:2 as there are 1.008 mols of CoCl2 and 1.952 mol of H₂O. Thus formula is CoCl₂.2 H₂O