Question

For a CoCl2 hydrate, there's .74 grams of water and .88 grams of anhydrate. How do I figure out the formula?

Answer 1

Divide the mass of water and anhydrate by the molecular masses of water and CoCl2 respectively to get the number of moles.
H2O:
\[\frac{ 0.74 }{ 18 }= 0.0411\]
CoCl2:
\[\frac{ 0.88 }{ 129.8 }= 0.006779\]

Answer 2

Now for the formula of the hydrate, you need to write it as CoCl2.xH2O

To find the x:

0.006779 moles of Cocl2 combine with 0.041 moles of water.
I mole of CoCl2 will combine with x moles of water?

x= \[\frac{ 0.04111 }{ 0.006779}= 6.06\]

So the formula will be \[CoCl _{2}. 6H _{2}O\]