Limiting and Excess Reagents in Chemical Reactions

Limiting Reagent

Substance consumed first in a chemical reaction.

Excess Reagent

Substance remaining after the reaction completes.

Balanced Chemical Reaction

Equation representing conservation of mass in reactions.

Molar Mass of Carbon

12.01 g/mol for Carbon (C).

Molar Mass of Oxygen

31.9989 g/mol for Oxygen (O₂).

Molar Mass of Carbon Dioxide

44.009 g/mol for Carbon Dioxide (CO₂).

Actual Yield (AY)

Mass of product actually produced in an experiment.

Theoretical Yield (TY)

Maximum mass of product calculated from stoichiometry.

Percent Yield (%Y)

Ratio of AY to TY multiplied by 100.

Stoichiometry

Calculation of reactants and products in reactions.

Mass of CO₂

Calculated from moles and molar mass of CO₂.

Molar Ratio

Proportional relationship between reactants and products.

Percent Yield Calculation

Formula: %Y = (AY/TY) x 100.

Experimental Errors

Factors causing lower than expected yields.

Mass of N₂

15.01 g for nitrogen in the reaction.

Mass of NH₃

Calculated from moles of NH₃ produced.

Theoretical Yield of NH₃

Calculated from 15 g of N₂.

Final Answer Dependence

Final yield depends on limiting reagent identified.

Molar Mass of NH₃

17.031 g/mol for Ammonia (NH₃).

Mass of Product Calculation

Use moles and molar mass to find mass.

Ethanol Yield Example

TY of 50.5g with %Y of 64.25%.

Actual Yield from Percent Yield

AY = (TY x %Y) / 100.