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Ch.4 - Chemical Quantities & Aqueous Reactions
Chapter 4, Problem 35

For each of the acid–base reactions, calculate the mass (in grams) of each acid necessary to completely react with and neutralize 4.85 g of the base. b. 2 HNO3(aq) + Ca(OH)2(aq) → 2 H2O(l) + Ca(NO3)2(aq)

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Identify the balanced chemical equation: 2 \text{HNO}_3(aq) + \text{Ca(OH)}_2(aq) \rightarrow 2 \text{H}_2\text{O}(l) + \text{Ca(NO}_3\text{)}_2(aq)
Calculate the molar mass of the base, \text{Ca(OH)}_2, using the periodic table: \text{Ca} = 40.08 \, \text{g/mol}, \text{O} = 16.00 \, \text{g/mol}, \text{H} = 1.01 \, \text{g/mol}
Determine the number of moles of \text{Ca(OH)}_2 in 4.85 \, \text{g} by dividing the mass by the molar mass of \text{Ca(OH)}_2.
Use the stoichiometry of the balanced equation to find the moles of \text{HNO}_3 needed. According to the equation, 2 moles of \text{HNO}_3 react with 1 mole of \text{Ca(OH)}_2.
Calculate the mass of \text{HNO}_3 required by multiplying the moles of \text{HNO}_3 by its molar mass (\text{H} = 1.01 \, \text{g/mol}, \text{N} = 14.01 \, \text{g/mol}, \text{O} = 16.00 \, \text{g/mol}).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It involves using mole ratios derived from the coefficients of the balanced equation to determine the amount of substances needed or produced. In this case, stoichiometry will help calculate the mass of nitric acid required to neutralize a given mass of calcium hydroxide.
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Acid-Base Neutralization

Acid-base neutralization is a chemical reaction where an acid reacts with a base to produce water and a salt. This process typically involves the transfer of protons (H+) from the acid to the base. Understanding the nature of the reactants, such as HNO3 being a strong acid and Ca(OH)2 being a strong base, is essential for predicting the products and calculating the amounts needed for complete reaction.
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Molar Mass

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is crucial for converting between grams and moles in stoichiometric calculations. To find the mass of nitric acid needed, one must first determine its molar mass and then use it in conjunction with the stoichiometric ratios from the balanced equation to find the required mass to neutralize the specified amount of base.
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