How many grams of Al(OH)₃ are required to neutralize 150. mL of stomach acid with a pH of 1.5?

Verified step by step guidance

1. Step 1: Calculate the concentration of hydrogen ions ([H⁺]) in the stomach acid using the pH formula: \( \text{pH} = -\log[H^+] \). Rearrange the formula to find \( [H^+] = 10^{-\text{pH}} \), and substitute \( \text{pH} = 1.5 \) to determine \( [H^+] \).
2. Step 2: Determine the moles of hydrogen ions in the stomach acid. Use the formula \( \text{moles of } H^+ = [H^+] \times \text{volume in liters} \). Convert the given volume of 150. mL to liters by dividing by 1000.
3. Step 3: Write the balanced chemical equation for the reaction between aluminum hydroxide (Al(OH)₃) and hydrogen ions (H⁺): \( \text{Al(OH)}_3 + 3H^+ \rightarrow \text{Al}^{3+} + 3H_2O \). From the equation, note that 1 mole of Al(OH)₃ reacts with 3 moles of H⁺.
4. Step 4: Calculate the moles of Al(OH)₃ required to neutralize the stomach acid. Use the stoichiometric ratio from the balanced equation: \( \text{moles of Al(OH)}_3 = \frac{\text{moles of } H^+}{3} \).
5. Step 5: Convert the moles of Al(OH)₃ to grams. Use the molar mass of Al(OH)₃ (\( \text{Al: 26.98 g/mol, O: 16.00 g/mol, H: 1.008 g/mol} \)) to calculate its molar mass, then multiply the moles of Al(OH)₃ by the molar mass to find the mass in grams.

Key Concepts

Neutralization Reaction

A neutralization reaction occurs when an acid reacts with a base to produce water and a salt. In this context, aluminum hydroxide (Al(OH)₃) acts as a base that will react with the hydrochloric acid (HCl) present in stomach acid. The balanced chemical equation for this reaction is Al(OH)₃ + 3HCl → AlCl₃ + 3H₂O, which is essential for calculating the amount of Al(OH)₃ needed.

pH and Hydrogen Ion Concentration

pH is a measure of the acidity or basicity of a solution, defined as the negative logarithm of the hydrogen ion concentration. A pH of 1.5 indicates a highly acidic solution, with a hydrogen ion concentration of approximately 0.0316 M. Understanding the relationship between pH and hydrogen ion concentration is crucial for determining how much base is needed to neutralize the acid.

Stoichiometry

Stoichiometry involves the calculation of reactants and products in chemical reactions based on the balanced equation. It allows us to determine the exact amount of Al(OH)₃ required to neutralize the given volume of stomach acid. By using the molarity of the acid and the stoichiometric coefficients from the balanced equation, we can calculate the grams of Al(OH)₃ needed for complete neutralization.