How would I go about determining the formula and name of this?
A hydrate of Na2CO3 has a mass of 4.31 g before heating. After heating, the mass of the anhydrous compound is found to be 3.22 g.

Question

How would I go about determining the formula and name of this? 
A hydrate of Na2CO3 has a mass of 4.31 g before heating. After heating, the mass of the anhydrous compound is found to be 3.22 g.

welshfella · Answer

we can write the formula for the hydrate as Na2CO3x H2O  where x is a whole number and is the number of molecules of water in the hydrate.

welshfella · Answer

The molecular mass od Na2CO3 = 105.99
and Molecular mass of H2O is  18.008

welshfella · Answer

in the experiment 4.31 g of the hydrate after heating formed 3.22 g of Na2CO3. The difference in mass is due to the loss of H2O.
Mass of H2O lost = 4.31 - 3.22 = 1.09 g

Now to find the ratio of molecules of Na2CO3 to water we divide 
3.22 and 1.09  by their respective molecular masses
3.22 / 105.99 =  0.03038
1.09 / 18.016 =  0.06050

- which is very close to 1 : what?
the second number is the value of x