Question 1

What is percent yield?

Accepted Answer

Percent yield measures the efficiency of a chemical reaction by comparing the actual product obtained to the maximum possible (theoretical) product. % yield = (actual / theoretical) × 100.

Question 2

Why is percent yield usually less than 100%?

Accepted Answer

Yields below 100% are caused by incomplete reactions, side reactions, product loss during purification, transfer losses, and measurement errors. It is rare to achieve exactly 100% yield.

Question 3

Can percent yield exceed 100%?

Accepted Answer

A true chemical reaction cannot produce more than 100% of the theoretical yield. Values above 100% usually indicate impurities in the product, residual solvent, incomplete drying, or calculation errors.

Question 4

How do I find the theoretical yield?

Accepted Answer

Use stoichiometry: (1) find moles of limiting reagent, (2) use the mole ratio to find moles of product, (3) convert moles of product to grams using the product's molar mass. This gives the maximum possible product.

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