Formula of hydrated mg sulfate?

Question

In an attempt to determine the formula of hydrated magnesium sulfate a student

obtained the following data

Mass of empty crucible

=12.500 g

Mass of crucible+hydrate

=15.935 g

Mass of crucible+anhydrate = 14.175 g

1) Calculate the percentage of water in the hydrate?

2) The molar mass of the anhydrate is 120.3 g/mol determine the formula ofthe hydrate by computing moles of water / moles of anhydrate

Answer 1

Subtract the crucible from the mass of crucible - hydrate and you have the mass of the hydrate

Subtract the last 2 numbers and you have the mass of the water that was driven off.

Take a percentage of the mass of the water against the hydrate and you have the percentage answer.

Now calculate the way you would solve for an empirical formula problem. Divide the percentage of the anhydride by 120.3 and the percentage of the water by 18. Convert to whole number ratio.

I believe the answer is MgSO4-7H2O