Let's break down each statement carefully to determine which one accurately describes the actual yield and the theoretical yield of a reaction.
1. First Statement:
- "The actual yield is calculated from the reactant amounts, but the theoretical yield must be measured for each instance of a reaction."
- This statement is incorrect because the actual yield is measured from experimental results, while the theoretical yield is calculated based on stoichiometry from the reactant amounts.
2. Second Statement:
- "The actual yield is calculated from the amount of the limiting reactant, and the theoretical yield is calculated from the amount of the excess reactant."
- This statement is incorrect because both actual yield and theoretical yield are based on the limiting reactant. The theoretical yield is the maximum amount of product that can be formed from the limiting reactant, while the actual yield is the amount of product actually obtained from the experiment.
3. Third Statement:
- "The actual yield depends on the reaction conditions, but the theoretical yield varies only with reactant amounts."
- This is the correct statement. The theoretical yield is calculated based on the balanced chemical equation and the amounts of reactants used, assuming a perfect reaction with no losses. The actual yield, however, depends on the actual conditions under which the reaction is carried out, including inefficiencies and losses that occur in practical scenarios.
4. Fourth Statement:
- "The actual yield represents the maximum yield possible, and the theoretical yield assumes perfect reaction conditions."
- This statement is incorrect because it is the theoretical yield that represents the maximum yield possible under perfect conditions. The actual yield is what is actually obtained from the reaction, which is often less than the theoretical yield due to various losses and inefficiencies.
Therefore, the correct statement is: "The actual yield depends on the reaction conditions, but the theoretical yield varies only with reactant amounts."
