Reaction Yield

Stoichiometric Amounts

• The relative amounts of reactants and products represented by a balanced chemical equation.

• Correspond to the mole ratios given by the coefficients

• Ensure complete consumption of all reactants with no leftovers

• Form the basis of stoichiometric calculations.

Limiting Reactant (Limiting Reagent)

• The reactant that is completely consumed first in a chemical reaction

• Determines the maximum amount of product that can be formed

• Stops the reaction once it is exhausted

• Produces the smallest theoretical yield of product when analyzed separately.

Excess Reactant (Excess Reagent)

• The reactant present in a quantity greater than required by stoichiometry

• Remains partially unreacted after the reaction is complete

• Does not determine the amount of product formed

• Left over once the limiting reactant is consumed

Stoichiometric Ratio

• The mole ratio between reactants or products given by a balanced chemical equation

• Used to determine whether reactants are present in correct proportions

• Essential for identifying the limiting reactant.

Convert all reactants to moles, then compare the actual mole ratio to the stoichiometric mole ratio, and then the reactant that runs out first is the limiting reactant

Method 1 for Identifying the Limiting Reactant

Calculate how much product each reactant could theoretically produce, after that, compare the amounts of product formed. The reactant yielding the smaller amount of product is the limiting reactant

Method 2 for Identifying the Limiting Reactant

Product-Yield Method

• A limiting-reactant technique in which each reactant is treated separately to determine theoretical product formation

• The smaller product amount identifies the limiting reactant

Complete Consumption

• The state in which a reactant is entirely used up during a reaction

• Characteristic of the limiting reactant.

Nonstoichiometric Amounts

• Reactant quantities that do not match the ratios required by the balanced equation

• Result in one reactant being limiting and another being in excess

Theoretical Yield

• The maximum amount of product predicted by stoichiometric calculations

• Assumes complete reaction and no losses

• Determined from the limiting reactant

• Represents the best possible outcome

Actual Yield

• The amount of product actually obtained in an experiment.

• Usually less than the theoretical yield

• Measured experimentally

• Affected by reaction inefficiencies and product losses.

Percent Yield

• A measure of how efficiently a reaction produces the desired product.

• Compares actual yield to theoretical yield

• Expressed as a percentage

Percent Yield = ((Actual Yield)/(Theoretical Yield))*100%

Percent Yield Formula

Reasons for Why Actual Yield is Often Less Than Theoretical Yield

• Side reactions may form unwanted products

• Reactions may not go to completion

• Product may be lost during purification or collection

• Experimental errors may occur

Side Reaction

• An undesired reaction occurring alongside the main reaction

• Consumes reactants that could otherwise form the desired product.

• Reduces actual yield

Incomplete Reaction

• A reaction that does not consume all available limiting reactant

• Produces less product than theoretically predicted

• Lowers percent yield.

Product Recovery Loss

• Loss of product during filtration, transfer, purification, or handling

• Causes actual yield to be less than theoretical yield.

limiting reactant, excess reactant

The theoretical yield must always be calculated from the ________________. The _____________ cannot determine maximum product formation.