# Homework Help: Calculating theoretical yield of resulting alum from water dissolving help asap!

1. Nov 9, 2008

### curlyfries4

calculating theoretical yield of resulting alum from water dissolving....help asap!

a mass of 13.02g (NH4)2SO4 is dissolved in water. After the solution is heated, 27.22g of Al2(SO4)3*18H2O is added. calculate the theoretical yield of the resulting alum (formula is NH4+(superscript)Al3+(superscript)(SO4)2*12H2O) Hint:this is a limiting reactant problem.

so far ive got 2Al+(NH4)2SO4+H2O yields Al2(SO4)3*18H2O + the formula of alum but im rly not sure if this is right...please hellppp meeee asap!thanks.

2. Nov 11, 2008

### chemisttree

Re: calculating theoretical yield of resulting alum from water dissolving....help asa

Balance this first....

Al2(SO4)3*18H2O + (NH4)2SO4 -----> NH4Al(SO4)2ยท12H2O

3. Nov 11, 2008

### Staff: Mentor

Re: calculating theoretical yield of resulting alum from water dissolving....help asa

Note: you will need water on the LHS.

4. Nov 11, 2008

### curlyfries4

Re: calculating theoretical yield of resulting alum from water dissolving....help asa

but i dont know how to balance with hydrates that well...the limiting reactant side?

5. Nov 11, 2008

### Staff: Mentor

Re: calculating theoretical yield of resulting alum from water dissolving....help asa

Write hydrate as Al2(SO4)3(H2O)18. LH stands for left hand.