Question

10g of s react with excess of o2 to form 15g of so2. the % yield of the reaction is

Answer 1

Theoretical yield

The amount of product that could possibly be produced in a given reaction, calculated according to the starting amount of the limiting reagent.

Actual yield

The amount of product actually obtained in a chemical reaction.

% yield is calculated as follows:

(actual yield / theoretical yield )×100

Calculate the actual theoretical yield of the reaction:

S₂ + 2 O₂ = 2 SO₂

Moles of S₂moles = mass/molar mass        = 10/64       = 0.15625

Mole ratio between S:SO2  = 1:2

That means the moles of SO₂ = 2 x 0.15625 = 0.3125

Find theoretical mass of the SO₂

Mass = moles × molar mass         
          = 0.3125 × 64          = 20 g
Therefore:

Actual yield = 15g

Theoretical yield = 20g

% yield = 15 g /20 g  × 100%             
             = 0.75 × 100%             
              =   75%
The % yield  = 75%