Question

After determining the limiting reactant in a reaction, you calculate the amount of product that can form from the limiting reactant. Is this the theoretical yield or the actual yield?

Short answer

The amount of product calculated from the limiting reactant is the theoretical yield.

Step-by-step solution

Understand Concept of Limiting Reactant

The limiting reactant is the substance which runs out first in a chemical reaction. Once it is fully consumed, the reaction stops, preventing the formation of more product.

Conceptualize Theoretical Yield

Theoretical yield is the amount of product that would result from a chemical reaction if all of the limiting reactant reacted completely. It is calculated using stoichiometry.

Comparison with Actual Yield

The actual yield is the amount of product that is actually obtained from the chemical reaction. It is often less than the theoretical yield due to factors such as incomplete reactions, side reactions, and losses in handling.

Final Concept Clarification

The amount of product calculated from the limiting reactant is the theoretical yield, not the actual yield. The actual yield must be determined by conducting the reaction and measuring the amount of product obtained.

Key concepts

Theoretical Yield

When performing a chemical reaction, one of the key goals is to predict how much product can be formed. This prediction is known as the "theoretical yield." The theoretical yield is based on the chemical equation and provides the maximum amount of product expected, assuming complete conversion of the limiting reactant into the desired product.

To determine this yield, you utilize stoichiometry. By using balanced equations, you can convert mass or moles of the limiting reactant to mass or moles of the product. The assumptions made here are perfect conditions where reactants completely react without any side reactions.

However, remember that the theoretical yield is often a best-case scenario. Real-world conditions, like reaction inefficiencies, ensure that the actual yield is usually lower than what you calculated as the theoretical.

Actual Yield

The actual yield represents the real-world result of a chemical reaction. It is determined by measuring the amount of product actually produced when the reaction is performed. Unlike theoretical yield, actual yield accounts for all the practical realities of a chemical reaction.

A variety of factors can influence actual yield:

• Incomplete reactions where not all reactants convert to products.
• Side reactions that produce unwanted by-products.
• Practical losses during processing, collection, or purification of the product.

These factors typically cause the actual yield to be lower than the theoretical yield. The ratio of actual yield to theoretical yield, multiplied by 100, gives the percent yield, indicating the efficiency of the reaction.

Stoichiometry

Stoichiometry is the mathematical foundation of chemistry that deals with the relationships between the quantities of reactants and products in a chemical reaction. It enables chemists to predict the amounts of substances consumed and produced.

Using stoichiometry, you convert units of a given substance to units of another, often involving steps like:

• Converting masses to moles using molar mass.
• Using the mole ratios from balanced chemical equations to relate reactants to products.
• Converting moles back to masses or volumes if needed.

Understanding stoichiometry is essential for determining the theoretical yield, as it allows you to calculate how much product is expected from a given amount of reactant, taking the balanced reaction into full account.