Chapter: Stoichiometry Examples Question 3: Given the following reaction: 2 Al +

ID: 1036428 • Letter: C

Question

Chapter: Stoichiometry Examples

Question 3: Given the following reaction: 2 Al + 3Br2 _> 2AlBr3

If 44.2 grams of aluminum are mixed with 44.2 grams of bromine.

a) which chemical is the limiting reagent?

b) what is the theoretical yield of aluminum bromide?

c)If the actual yield of alumimum bromide was 47.6 grams, what was the percent yield?

Question 4: Given the following reaction: P4 + 6F2 > 4PF3

If 38.2 grams of phosphorous are mixed with 2.75 moles of fluordine.

a) which chemical is the limiting reagent?

b) what is the theoretical yield of phosphorous fluoride?

c)If the percent yield was 89.2%, what was the actual yield?

Thanks!

2 Al + 3Br2 ----> 2AlBr3

no of moles of Al = W/G.A.Wt

= 44.2/27 = 1.637 moles

no of moles of Br2 = W/G.M.Wt

= 44.2/160 = 0.27625moles

2 moles of Al react with 3 moles of Br2

1.637 moles of Al react with = 3*1.637/2 = 2.4555moles of Br2 is required.

Br2 is limiting reactant

3 moles of Br2 react with AL to gives 2moles of AlBr3

0.27625 moles of Br2 react with Al to gives = 2*0.27625/3 = 0.184 moles of AlBr3

mass of AlBr3 = no of moles * gram molar mass

= 0.184*267 = 49.128g

Theoretical yiled of AlBr3 = 49.128g

percent yiled = actual yiled*100/theoretical yiled

= 47.6*100/49.128 = 96.89%