Mole Concept and Stoichiometry?

📌 CONCEPT: The mole concept is used to relate the amount of a substance to its mass, and stoichiometry is the study of the quantitative relationships between reactants and products in chemical reactions.

📐 RULE / FORMULA: According to Avogadro's Law, equal volumes of gases at the same temperature and pressure contain an equal number of moles. The mole ratio of reactants to products is obtained from the balanced chemical equation.

💡 WORKED EXAMPLE: The balanced chemical equation for the reaction is: 2H2 + O2 → 2H2O. Given 16 grams of oxygen gas (O2), we need to find the number of moles of hydrogen gas (H2) required. First, we calculate the number of moles of oxygen gas using the molar mass of oxygen (32 g/mol): n(O2) = mass of O2 / molar mass of O2 = 16 g / 32 g/mol = 0.5 mol. According to the balanced equation, the mole ratio of H2 to O2 is 2:1. Therefore, the number of moles of hydrogen gas required is 2 × n(O2) = 2 × 0.5 mol = 1 mol.

⚠️ COMMON MISTAKE: Students often forget to use the mole ratio obtained from the balanced chemical equation, leading to incorrect calculations of the number of moles of reactants or products.