Question

when 42.66 grams of PCl5 react with excess P4O10 the amount of product formed is 47.22 grams of POCl3. What is the percent yield

Answer 1

Percent yield or yield is mathematically defined as:

Yield = Actual amount / Theoretical amount

So to solve the yield, let us first calculate the theoretical amount of POCl3 produced. The balanced chemical reaction for this is:

6 PCl5 + P4O10  --->  10 POCl3

Since P4O10 is stated to be supplied in large amount, then PCl5 becomes the limiting reactant.

So we calculate for POCl3 based on PCl5. To do this let us convert the amount into moles: (molar mass PCl5 = 208.24 g/mol)

n PCl5 = 42.66 grams / (208.24 g/mol)

n PCl5 = 0.205 mol

 

Now based on the stoichiometric ratio of the reaction:

n POCl3 = 0.205 mol (10 POCl3 / 6 PCl5)
n POCl3 = 0.3414 mol POCl3

Converting to mass (molar mass POCl3 = 153.33 g/mol)

m POCl3 = 0.3414 mol (153.33 g/mol)

m POCl3 = 52.35 g

 

Calculating for yield:

Yield = 47.22 g/ 52.35 g

Yield = 0.902

%Yield = 90.2 %                      (ANSWER)