A 25.0-mL sample of a 1.20 M potassium chloride solution is mixed with 15.0 mL of a 0.900 M lead(II) nitrate solution and this precipitation reaction occurs: 2 KCl(aq) + Pb(NO3)2(aq) → PbCl2(s) + 2 KNO3(aq). The solid PbCl2 is collected, dried, and found to have a mass of 2.45 g. Determine the limiting reactant and the theoretical yield.

Verified step by step guidance

1. Calculate the moles of KCl: Use the formula \( \text{moles} = \text{molarity} \times \text{volume in liters} \) to find the moles of KCl in the 25.0 mL solution.
2. Calculate the moles of Pb(NO3)2: Similarly, use the formula \( \text{moles} = \text{molarity} \times \text{volume in liters} \) to find the moles of Pb(NO3)2 in the 15.0 mL solution.
3. Determine the limiting reactant: Use the stoichiometry of the balanced equation, 2 KCl + Pb(NO3)2 → PbCl2 + 2 KNO3, to compare the mole ratio of the reactants and identify the limiting reactant.
4. Calculate the theoretical yield of PbCl2: Use the moles of the limiting reactant and the stoichiometry of the reaction to calculate the moles of PbCl2 that can be formed, then convert this to grams using the molar mass of PbCl2.
5. Compare the theoretical yield to the actual yield: The actual yield is given as 2.45 g. Compare this to the theoretical yield to assess the efficiency of the reaction.

Key Concepts

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It allows us to determine the proportions of substances involved in a reaction, which is essential for identifying the limiting reactant and calculating theoretical yields. In this case, the stoichiometric coefficients from the balanced equation indicate the molar ratios of KCl and Pb(NO3)2 needed to produce PbCl2.

Limiting Reactant

The limiting reactant is the substance that is completely consumed first in a chemical reaction, thus determining the maximum amount of product that can be formed. To identify the limiting reactant, one must compare the mole ratios of the reactants used in the reaction to the stoichiometric ratios from the balanced equation. The reactant that produces the lesser amount of product is the limiting reactant.

Theoretical Yield

The theoretical yield is the maximum amount of product that can be produced from a given amount of reactants, calculated based on the limiting reactant. It is determined using stoichiometric calculations from the balanced equation and the initial amounts of reactants. The actual yield, which is the amount of product obtained from the experiment, is often less than the theoretical yield due to various factors such as incomplete reactions or losses during processing.