Ch.4 - Reactions in Aqueous Solution

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.4 - Reactions in Aqueous Solution

Problem 52

Chapter 4, Problem 52

Copper reacts with dilute nitric acid according to the following equation: If a copper penny weighing 3.045 g is dissolved in a small amount of nitric acid and the resultant solution is diluted to 50.0 mL with water, what is the molarity of the Cu(NO3)2?

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Identify the balanced chemical equation for the reaction: \( \text{Cu} + 4\text{HNO}_3 \rightarrow \text{Cu(NO}_3\text{)}_2 + 2\text{NO}_2 + 2\text{H}_2\text{O} \).

Calculate the moles of copper (Cu) using its molar mass: \( \text{moles of Cu} = \frac{\text{mass of Cu}}{\text{molar mass of Cu}} \).

Use the stoichiometry of the balanced equation to find the moles of \( \text{Cu(NO}_3\text{)}_2 \) produced. Since 1 mole of Cu produces 1 mole of \( \text{Cu(NO}_3\text{)}_2 \), the moles of \( \text{Cu(NO}_3\text{)}_2 \) will be equal to the moles of Cu.

Calculate the molarity of \( \text{Cu(NO}_3\text{)}_2 \) using the formula: \( \text{Molarity} = \frac{\text{moles of solute}}{\text{volume of solution in liters}} \).

Convert the volume of the solution from milliliters to liters before using it in the molarity calculation.

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Key Concepts

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

Molarity

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in units of moles per liter (mol/L). To calculate molarity, one must know the amount of solute in moles and the total volume of the solution in liters. This concept is essential for determining how concentrated a solution is, which is crucial for understanding the behavior of chemical reactions in solution.

Stoichiometry

Stoichiometry involves the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It allows us to determine the amount of product formed or reactant consumed in a reaction. In this case, knowing the stoichiometric coefficients from the reaction between copper and nitric acid will help in calculating the moles of Cu(NO3)2 produced from the given mass of copper.

Dilution

Dilution is the process of reducing the concentration of a solute in a solution, typically by adding more solvent. The dilution equation, M1V1 = M2V2, relates the initial and final molarity and volumes of the solution. Understanding dilution is important for accurately calculating the final concentration of Cu(NO3)2 after the copper penny is dissolved and the solution is brought to a specific volume.

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