Question 1: What is a limiting reactant in a chemical reaction?

Answer: A limiting reactant is the substance that is completely consumed first in a chemical reaction, limiting the amount of product formed.

Question 2: Explain the mechanism by which a limiting reactant determines the maximum amount of product in a reaction.

Answer: The limiting reactant is entirely used up during the reaction, so the amount of product formed depends on its quantity, while other reactants are in excess.

Question 1: Given 10 grams of hydrogen gas (H₂) and 80 grams of oxygen gas (O₂), determine the limiting reactant when these gases react to form water (H₂O). Atomic masses: H = 1 g/mol, O = 16 g/mol. Write the calculations and identify the limiting reactant.

Answer: Moles of H₂ = 10 g / 2 g/mol = 5 mol; Moles of O₂ = 80 g / 32 g/mol = 2.5 mol. Reaction: 2H₂ + O₂ → 2H₂O. Required H₂ for 2.5 mol O₂ = 2 * 2.5 mol = 5 mol, which matches available H₂. Therefore, no limiting reactant; both are in perfect ratio.

Question 2: If 15 grams of aluminum (Al) reacts with 25 grams of sulfur (S), which reactant is limiting? Atomic masses: Al = 27 g/mol, S = 32 g/mol. Show your calculations.

Answer: Moles of Al = 15 g / 27 g/mol ≈ 0.556 mol; Moles of S = 25 g / 32 g/mol ≈ 0.781 mol. Reaction: 2Al + 3S → Al₂S₃. Moles of S needed for 0.556 mol Al = (3/2) * 0.556 ≈ 0.834 mol. Since only 0.781 mol S is available, S is limiting.

Question 1: A reaction involves 50 grams of reactant A and excess of reactant B. The product formed weighs 40 grams. If in another trial, 50 grams of reactant A produces only 25 grams of product, explain what this indicates about the limiting reactant.

Answer: The decrease in product yield suggests that in the second trial, reactant A was in excess, and reactant B became the limiting reactant, limiting the amount of product formed.

Question 2: In an industrial process, 100 kg of reactant X reacts with 150 kg of reactant Y to produce 200 kg of product. If the reaction yields only 150 kg of product under similar conditions, what can be inferred about the limiting reactant? Provide a brief explanation.

Answer: It indicates that one of the reactants is limiting, likely the one that was not in sufficient quantity to produce more product. The actual limiting reactant can be identified by comparing theoretical yields based on initial amounts.

Question 1: Describe the process of identifying the limiting reactant in a chemical reaction. Include the steps involved, necessary calculations, and how to interpret data to determine which reactant is limiting.

Answer: To identify the limiting reactant, first write the balanced chemical equation. Convert all reactants to moles using their molar masses. Calculate the mole ratio needed based on the balanced equation. Compare the actual mole quantities to the ratio; the reactant with the smallest amount relative to its required ratio is limiting. Finally, verify by calculating the maximum theoretical yield of the product from each reactant; the one producing the least amount of product is the limiting reactant.

Question 1: Explain how understanding limiting reactants is important in the manufacturing of pharmaceuticals.

Answer: Knowing the limiting reactant helps optimize the amounts of reactants used, reduce waste, and ensure maximum yield and cost-effectiveness in pharmaceutical production.

Question 2: Describe a real-life scenario where controlling limiting reactants can prevent accidents or environmental issues.

Answer: In chemical plants, controlling limiting reactants prevents excess reactants from reacting completely, which can produce hazardous by-products or release pollutants into the environment.