Question

PLEASE HELP!Suppose you begin with 1.50~g of the hydrate copper(II)sulfate · x-hydrate (CuSO4· x H2O), where x is an integer. After dehydration you find that you are left with 0.96~g of the an-hydrate CuSO4. What is the unknown integer x. Round your answer to the nearest integer, enter only an integer.
Suppose you begin with of the hydrate KAl(SO4)2 · 12H2O. After dehydration you find that you are left with 3.0~g of the an-hydrate KAl(SO4)2. How many grams did you start with? Write the value to the correct number of significance figures.

Answer 1

You have to made the difference between the weights before and after the dehydration. That is the amount of H2O by mass. Calculate how many moles of H2O do you lost .
Then calculate how many moles of the an-hydrate compound you have in the 0.96g. The realtionship between the moles of H2O/moles of un-hydrate will give you how many H2O molecules you will have by mole of hydrate that is the number x that you have to put in the formula.