Yield (Chemistry)

Key Stage 4

Meaning

Yield is the mass of product in a chemical reaction.

About Yield

The theoretical yield of product from a chemical reaction can be calculated using the balanced symbol equation and the relative formula masses of all the molecules involved.

The experimental yield from a chemical reaction is often not as large as the theoretical yield because not all of the reactants will react. This experimental yield is often expressed as a percentage of the theoretical yield and is known as the Percentage Yield.

Examples

Calculate the yield of Magnesium Oxide given 48g of Magnesium and excess Oxygen.	Find the yield of Water when 320g of Methane reacts with excess Oxygen.	Find the yield of Sodium Chloride when 7.3 of Hydrochloric Acid reacts with excess Sodium Hydroxide.
Write the Balanced Symbol Equation 2Mg + O2 → 2MgO	Write the Balanced Symbol Equation CH4 + 2O2 → 2H2O + CO2	Write the Balanced Symbol Equation NaOH + HCl → NaCl + H2O
Find the Relative Formula Mass of the relevant reactants and product. Mr of Mg = 24g Mr of MgO = 40g	Find the Relative Formula Mass of the relevant reactants and product. Mr of CH4 = 16g Mr of H2O = 18g	Find the Relative Formula Mass of the relevant reactants and product. Mr of NaOH = 40g Mr of HCl = 36.5g Mr of NaCl = 58.5g
State the ratio of moles of each chemical needed. 2 moles of Mg are needed for every 2 moles of MgO	State the ratio of moles of each chemical needed. 1 mole of CH4 is needed for every 2 moles H2O	State the ratio of moles of each chemical needed. 1 mole of HCl and NaOH are needed for every 1 mole of NaCl
Find the number of moles supplied of the known mass. No. Moles = \(\frac{Mass}{M_r}\) No. Moles = \(\frac{48}{24}\) No. Moles = 2 mol Therefore 2 moles of MgO is produced. 2 moles of MgO = 40x2 Yield = 80g	Find the number of moles supplied of the known mass. No. Moles = \(\frac{Mass}{M_r}\) No. Moles = \(\frac{320}{16}\) No. Moles = 20 mol Therefore 40 moles of H2O are produced. 40 moles of CO2 = 18x40 Yield = 720g	Find the number of moles supplied of the known mass. No. Moles = \(\frac{Mass}{M_r}\) No. Moles = \(\frac{7.3}{36.5}\) No. Moles = 0.2 mol Therefore 0.2 mole of Sodium Chloride is produced. 0.2 mole of NaCl = 11.7g Yield = 11.7g

References

AQA

Yield, page 66-7, GCSE Biology; Student Book, Collins, AQA

Yield, page 78, GCSE Chemistry, Hodder, AQA

Yield, pages 184-186, GCSE Combined Science Trilogy; Chemistry, CGP, AQA

Yield, pages 68-71, GCSE Chemistry; Third Edition, Oxford University Press, AQA

Yield, pages 97, 216-219, 317, 323, GCSE Chemistry; Student Book, Collins, AQA

Yields, pages 141, 144, 216-218, GCSE Chemistry, CGP, AQA

Yields, pages 45, 49, GCSE Chemistry; The Revision Guide, CGP, AQA