Need help urgent please :

1 Consider a sample containing 125 g of Na2SO4:
a) How many moles of Na2SO4 are present in the sample?
b) How many molecules of Na2SO4 are present in the sample?

2 Consider the following reaction: Fe O2 → Fe2O3
a) Balance the chemical equation
Consider the balanced equation and answer the following questions:
b) How many moles of O2 are necessary to react with 3 mol of Fe?
c) How many moles of O2 are necessary to react with 4.60 g of Fe?

3 Consider the following reaction: Sb2S3 HCl ï‚® SbCl3 H2S.
a) Balance the chemical equation
Consider the balanced equation and answer the following questions
If there are 40 g of Sb2S3:
b) How many grams of HCl are necessary to react with that amount of Sb2S3?
c) How many moles of H2S will be formed?
d) How many molecules of H2S will be formed?

4 Consider the following reaction: Al2(SO4)3 KOH ï‚® Al(OH)3 K2SO4
a) Write the balanced chemical equation.
Consider the balanced equation and answer the following questions:
b) How many grams of KOH are needed to react with 0.5 moles of Al2(SO4)3?
c) How many moles of K2SO4 will be obtained from 10 g of Al2(SO4)3?
d) How many molecules of Al(OH)3 will be obtained from 10 g of Al2(SO4)3?

5 Consider the following reaction: Na3PO4 (aq) Ba(NO3)2 (aq) ï‚® Ba3(PO4)2 (s) NaNO3 (aq)
a) Write the balanced chemical equation.
b) Using the balanced chemical equation, answer the following question: suppose a solution containing 3.5 g of Na3PO4 is mixed with a solution containing 6.4 g of Ba(NO3)2. How many grams of Ba3(PO4)2 can be formed? (Hint: you will need to read on a concept called limiting reagent).