Which quantity compares the actual yield to the theoretical yield and is expressed as a percentage?

• A. Limiting reagent
• B. Percent yield
• C. STP
• D. PV = nRT

Answer: (B)

Percent yield is the measure that compares how much product you actually obtained to the maximum amount that could be produced from the reaction, expressed as a percentage. The actual yield is the quantity you recover in the lab, while the theoretical yield comes from stoichiometric calculations based on the limiting reagent. By dividing the actual yield by the theoretical yield and multiplying by 100, you get the percent yield. This metric is useful for assessing reaction efficiency and identifying losses from incomplete reactions, side reactions, or purification steps. The limiting reagent concept helps determine the theoretical yield, but it is not itself a percentage. STP and PV = nRT are about gas properties and behavior, not about yield.