Final answer:
The ability to calculate theoretical yield is based on Dalton's postulate that atoms combine in simple, whole-number ratios, allowing the prediction of product amounts formed in a chemical reaction. Percent yield is then calculated using the actual yield and theoretical yield.
Step-by-step explanation:
The postulate of Dalton's atomic theory that explains why we can calculate a theoretical yield for a chemical reaction is that atoms combine in simple, whole-number ratios (Postulate 3).
This allows chemists to determine the amounts of reactants needed to form a product in whole-number proportions, and predict the amount of product that will be formed when the reactants completely react according to the balanced chemical equation. This concept is exemplified when calculating percent yield, which is the ratio of actual yield to theoretical yield, expressed as a percentage.
To calculate the percent yield, use the formula: Percent Yield = (Actual Yield / Theoretical Yield) × 100%. For instance, if a student isolated 25 g of a compound with a theoretical yield of 81 g, their percent yield would be (25 g / 81 g) × 100% = 30.86%. For the decomposition of calcium carbonate, where 0.53 g of carbon dioxide was obtained from 1.31 g of calcium carbonate, you would need the theoretical yield to determine the percent yield.