Which of the following correctly describes how to calculate percent error in a chemical experiment?

• A. Percent error = (theoretical value - experimental value) / experimental value × 100%
• B. Percent error = (actual yield / theoretical yield) × 100%
• C. Percent error = (experimental value - theoretical value) / theoretical value × 100%
• D. Percent error = (experimental value / theoretical value) × 100%

Answer: (C)

Verified step by step guidance

1. Understand that percent error is a measure of how far an experimental value deviates from a theoretical or accepted value, expressed as a percentage.
2. Recall the general formula for percent error: \(\text{Percent Error} = \frac{\left| \text{Experimental Value} - \text{Theoretical Value} \right|}{\text{Theoretical Value}} \times 100\%\).
3. Note that the numerator is the absolute difference between the experimental and theoretical values to ensure the error is always positive.
4. Recognize that the denominator is the theoretical value because percent error compares the deviation relative to the accepted or expected value.
5. Conclude that the correct formula matches the option: \(\text{Percent Error} = \frac{\text{Experimental Value} - \text{Theoretical Value}}{\text{Theoretical Value}} \times 100\%\), where the difference is taken as absolute value.