Which of the following statements best explains why a percent yield of 85% for a chemical reaction is considered reasonable?

• A. Some product may be lost during purification or transfer, so yields less than 100% are common.
• B. Percent yield is unrelated to experimental technique and always depends only on the theoretical yield.
• C. Percent yield should always be exactly 100% if the reaction is performed correctly.
• D. A percent yield above 100% is expected due to measurement errors.

Answer: (A)

Verified step by step guidance

1. Understand that percent yield is a measure of the efficiency of a chemical reaction, calculated by comparing the actual amount of product obtained (actual yield) to the maximum possible amount predicted by stoichiometry (theoretical yield). The formula is: \(\text{Percent Yield} = \left( \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \right) \times 100\%\).
2. Recognize that in practical laboratory settings, it is common to have a percent yield less than 100% because some product can be lost during steps such as purification, transfer between containers, or incomplete reactions.
3. Note that a percent yield exactly equal to 100% is ideal but rarely achieved due to these practical limitations and experimental errors.
4. Understand that percent yields greater than 100% usually indicate errors such as impurities in the product or measurement inaccuracies, not a true increase in product amount.
5. Conclude that a percent yield of 85% is reasonable and expected because it reflects typical losses and inefficiencies in the experimental process, making the statement about product loss during purification or transfer the best explanation.