STOIC %YIELD

NOT ANOTHER STOIC PROBLEM

1) Barium sulfate, BaSO4, is made by the following reaction:


Ba(NO3)2(aq) + Na2SO4(aq) à BaSO4(s) + 2NaNO3(aq)
An experiment was begun with 75.00g of Ba(NO3)2 and an excess of Na2SO4. After collecting and drying the product, 63.45g BaSO4 was obtained. Calculate the theoretical yield and percent yield of BaSO4.



2) Aluminum sulfate can be made by the following reaction:
2AlCl3(aq) + 3H2SO4(aq) à Al2(SO4)3(aq) + 6HCl(aq)
It is quite soluble in water, so to isolate it the solution has to be evaporated to dryness. This drives off the volatile HCl, but the residual solid has to be treated to a little over 200°C to drive off all the water. In one experiment, 25.0g of AlCl3 was mixed with 30.0g H2SO4. Eventually, 28.46g of pure Al2(SO4)3 was isolated. Calculate the percent yield.

ANSWERS:

1.) theoretical yield = 66.98g BaSO4, % yield = 94.73%
2.) % yield = 88.74%

STOICH 2

 _{EASY STOICHIOMETRY PROBLEMS}

1)      How many moles of sodium atoms correspond to 1.56x10²¹ atoms of sodium?

2)      How many moles of Al atoms are needed to combine with 1.58 mol of O atoms to make aluminum oxide, Al₂O₃?

3)      How many moles of Al are in 2.16 mol of Al₂O₃?

4)      Aluminum sulfate, Al₂(SO₄)₃, is a compound used in sewage treatment plants. 

a.     Construct a pair of conversion factors that relate moles of aluminum to moles of sulfur for this compound

b.     Construct a pair of conversion factors that relate moles of sulfur to moles of Al₂(SO₄)₃

c.       How many moles of Al are in a sample of this compound if the sample also contains 0.900 mol S?

d.     How many moles of S are in 1.16 mol Al₂(SO₄)₃?

5)      How many moles of H₂ and N₂ can be formed by the decomposition of 0.145 mol of ammonia, NH₃?

ANSWERS:

1)      2.59x10^-3mol Na atoms  

2)      1.05mol Al                

3)      4.32mol Al

4)      a. 2mol Al/3mol S            b. 3mol S/1mol Al₂(SO₄)₃            c. 0.600mol Al     d. 3.48mol S

5)      0.0725mol N₂ and 0.218mol H₂

EASY STOIC PROBLEMS

 _{EASY STOICHIOMETRY PROBLEMS}

1)      How many moles of sodium atoms correspond to 1.56x10²¹ atoms of sodium?

2)      How many moles of Al atoms are needed to combine with 1.58 mol of O atoms to make aluminum oxide, Al₂O₃?

3)      How many moles of Al are in 2.16 mol of Al₂O₃?

4)      Aluminum sulfate, Al₂(SO₄)₃, is a compound used in sewage treatment plants. 

a.     Construct a pair of conversion factors that relate moles of aluminum to moles of sulfur for this compound

b.     Construct a pair of conversion factors that relate moles of sulfur to moles of Al₂(SO₄)₃

c.       How many moles of Al are in a sample of this compound if the sample also contains 0.900 mol S?

d.     How many moles of S are in 1.16 mol Al₂(SO₄)₃?

5)      How many moles of H₂ and N₂ can be formed by the decomposition of 0.145 mol of ammonia, NH₃?

ANSWERS:

1)      2.59x10^-3mol Na atoms  

2)      1.05mol Al                

3)      4.32mol Al

4)      a. 2mol Al/3mol S            b. 3mol S/1mol Al₂(SO₄)₃            c. 0.600mol Al     d. 3.48mol S

5)      0.0725mol N₂ and 0.218mol H₂

STOICHIOMETRY