AP Chem help PLEASE PLEASE PLEASE!!!?

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AP Chem help PLEASE PLEASE PLEASE!!!?



I have a few problems i have been stuck on for days now and i need to find out what i am doing wrong and im doing this as sort of a last resort type thing so please answer asap i will put attempted answers to the side of each question. 

1. For the reaction (attempted: 11.89, 79.8) 
? Fe + ? H2O → ? Fe3O4+? H2 , 
what is the maximum amount of Fe3O4 which 
could be formed from 10.31 g of Fe and 
5.06 mol of H2O? 
Answer in units of g. 

2.For the reaction (attempted:1.6) 
? C6H6 + ? O2 ⇀↽? CO2 + ? H2O 
a maximum of ? moles of CO2 could be 
formed from 3.63 mol of C6H6 and 5.76 mol 
of O2. 
Answer in units of mol. 

3. For the reaction (attempted: 2.46) 
? Al + ? CuSO4 ⇀↽ ? Al2(SO4)3+? Cu 
a maximum of how many moles of Al2(SO4)3 
could be formed from 7.38 mol of Al and 
5.61 mol of CuSO4? 
Answer in units of mol. 

4. ? N2 + ? H2 → ? NH3 , (attempted: 31.4) 
what is the maximum amount of NH3 
(17.0305 g/mol) which could be formed from 
15.7 g of N2 (28.0134 g/mol) and 0.269 mol of 
H2 (2.01588 g/mol)? 
Answer in units of mol



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Posted Answers:

2. 
2 C6H6 + 15 O2 → 12 CO2 + 6 H2O 
5.76 moles of O2 would react completely with 5.76 x (2/15) = 0.768 mole of C6H6, but there is more C6H6 present than that, so C6H6 is in excess and O2 is the limiting reactant. 
(5.76 mol O2) x (12 mol CO2 / 15 mol O2) = 4.61 mol CO2 

3. 
2 Al + 3 CuSO4 → Al2(SO4)3 + 3 Cu 
5.61 moles of CuSO4 would react completely with 5.61 x (2/3) = 3.74 moles of Al, but there is more Al present than that, so Al is in excess and CuSO4 is the limiting reactant. 
(5.61 mol CuSO4) x (1 mol Al2(SO4)3 / 3 mol CuSO4) = 1.87 mol Al3(SO4)3