(d) If 42.7 mL of 0.208 M HCl solution is needed to neutralize a solution of Ca(OH)₂, how many grams of Ca(OH)₂ must be in the solution?

Key Concepts

Neutralization Reaction

A neutralization reaction occurs when an acid reacts with a base to produce water and a salt. In this case, hydrochloric acid (HCl) reacts with calcium hydroxide (Ca(OH)2). The balanced chemical equation for this reaction is 2 HCl + Ca(OH)2 → CaCl2 + 2 H2O, indicating that two moles of HCl are required to neutralize one mole of Ca(OH)2.

Molarity and Volume Relationship

Molarity (M) is defined as the number of moles of solute per liter of solution. To find the number of moles of HCl used in the reaction, you can use the formula: moles = molarity × volume (in liters). In this problem, the volume of HCl is given in milliliters, so it must be converted to liters before calculating the moles.

Stoichiometry

Stoichiometry involves using the coefficients from a balanced chemical equation to relate the amounts of reactants and products. In this case, knowing the moles of HCl allows you to determine the moles of Ca(OH)2 that reacted, and subsequently, you can convert moles of Ca(OH)2 to grams using its molar mass. This is essential for solving the problem accurately.