How to Calculate Theoretical Yield of a Reaction?
The Correct Answer and Explanation is:
To calculate the theoretical yield of a reaction, follow these steps:
- Write a balanced chemical equation: Identify the reactants and products and balance the equation to ensure that atoms are conserved on both sides.
- Identify the limiting reactant: Determine which reactant will be used up first, as this limits the amount of product that can be formed. Use stoichiometric coefficients to compare the mole ratios of the reactants.
- Calculate moles of the limiting reactant: Convert the amount of the limiting reactant (given in grams, if necessary) to moles using its molar mass.
- Use stoichiometry to find moles of the product: Apply the mole ratio from the balanced equation to determine how many moles of product are expected from the limiting reactant.
- Convert moles of product to grams: Use the product’s molar mass to convert from moles to grams, yielding the theoretical yield in grams.
Example: For the reaction ( 2H_2 + O_2 \rightarrow 2H_2O ):
- Suppose you start with 10 g of ( H_2 ) and 10 g of ( O_2 ).
- Calculate moles of each: Molar mass of ( H_2 = 2 ) g/mol, so ( 10 ) g ( H_2 = 5 ) mol. Molar mass of ( O_2 = 32 ) g/mol, so ( 10 ) g ( O_2 = 0.3125 ) mol.
- From the balanced equation, ( 2 ) mol ( H_2 ) reacts with ( 1 ) mol ( O_2 ). Therefore, ( O_2 ) is the limiting reactant because you have less than enough to react with all the ( H_2 ).
- Using stoichiometry, ( 1 ) mol ( O_2 ) yields ( 2 ) mol ( H_2O ), so ( 0.3125 ) mol ( O_2 ) would theoretically yield ( 0.625 ) mol ( H_2O ).
- Convert to grams: ( H_2O ) has a molar mass of ( 18 ) g/mol, so ( 0.625 ) mol ( H_2O = 11.25 ) g.
The theoretical yield is 11.25 g of ( H_2O ).
Explanation: Theoretical yield calculations allow chemists to predict the maximum amount of product achievable from specific reactant amounts. The limiting reactant dictates how far the reaction can proceed since it is entirely consumed first. Stoichiometric relationships provide the foundation, utilizing molar masses and mole ratios from the balanced reaction. Accurate yield predictions are essential in planning and optimizing reactions, especially in industrial applications, where maximizing product efficiency minimizes costs and resources.