Confusing-1.00g sample of an unkown hydrate of cobalt chloride is gently dehydrated the resulting mass is....?

Question

resulting mass is 0.546g.the cobalt is isolated and weighs 0.248g.what is the formula of the hydrate?
A)DETERMINE the number of moles of water lost from the hydrated unkown
B)DETERMINE the number of moles of cobalt collected
C)DETERMINE the number of moles of chloride in the compound
d)What is the mole ratio of cobalt to chloride(cobalt is equal to 1: )
E)WHAT is the mole ratio of cobalt to water lost (set cobalt to 1: )

Answer 1

The mass of water removed from the hydrate is 1.000 g - 0.546 g = 0.454 grams

The mass of chloride in the cobalt compound is 0.546g - 0.248 g = 0.298 g

Now, convert all the masses you have into moles:

Moles Co = 0.248/58.93 = 4.2 X 10^-3 mol Co
Moles Cl = 0.298/35.45 = 8.4 X 10^-3 mol Cl
Moles H2O = 0.454/18 = 0.0252 mol water.

Now, divide all of the moles by the moles of Co. That will give you the ratios you are after:
Co = 1
Cl = 2
H2O = 6

So, the final formula of the hydrate (your other question) is:

CoCl2*6H2O