Question

If a reaction has 1 mole of a starting compound reacts to give 1 mole of product, what is the percent yield of the product? 1.28 mL of the starting compound gives 0.5601 g of the product. The starting compound density is 0.91 g/mL, the starting compound molecular weight is 185.4 g/mol, and the product molecular weight is 111.8 g/mol.

Answer 1

Percentage yield of a reaction expresses the efficiency of a reaction. If a reaction have 100% yield , indicates that all the reactants are transformed into products. Percentage yield can be found out using the formula,

% yield = ( actual yield / theoretical yield ) × 100

Theoretical yield is the amount of product that should be form when the limiting reagent is completely consumed. Actual yield is the amount of product actually isolated from a reaction.

In this question 1 mole of reactant (R) forms 1mole of product (P) . That is, R   P

Mass of R = density × volume

= 1.28 ml × 0.91 g/ml

= 1.1648 g

Mass of P = 0.5601 g ( This is the actual yield )

Molar mass of R = 185.4 g/mol

Molar mass of P = 111.8 g/mol

Theoretical yield =

mass of reactant × { [ 1 mole of reactant / molecular mass of reactant ] × [ number of moles of product / number of moles of reactant ] × [ molecular mass of product / 1 mole of product] }

Theoretical yield =

1.1648 g × { [ 1 mole R / 185.4 g ] × [ 1 mole P / 1 mole R ] × [ 111.8 g / 1 mole P ] }

= 0.7024 g

Percentage yield = ( actual yield / theoretical yield ) × 100

= ( 0.5601 g / 0.7024 g ) × 100

= 79.7%