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Ch.9 Solutions
McMurry - Fundamentals of GOB 8th Edition
McMurry8th EditionFundamentals of GOBISBN: 9780134015187Not the one you use?Change textbook
Chapter 9, Problem 48

What is the mass/volume percent concentration of the following solutions?
a. 0.078 mol KCl in 75 mL of solution
b. 0.044 mol sucrose (C12H22O11) in 380 mL of solution

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Step 1: Recall the formula for mass/volume percent concentration: \( \text{Mass/Volume Percent} = \frac{\text{Mass of solute (g)}}{\text{Volume of solution (mL)}} \times 100 \).
Step 2: For part (a), calculate the mass of KCl. Use the molar mass of KCl (\( 39.10 \ \text{g/mol} \) for K and \( 35.45 \ \text{g/mol} \) for Cl) to find the mass of 0.078 mol of KCl: \( \text{Mass of KCl} = \text{Moles of KCl} \times \text{Molar Mass of KCl} \).
Step 3: Substitute the calculated mass of KCl and the given volume of solution (75 mL) into the mass/volume percent formula: \( \text{Mass/Volume Percent} = \frac{\text{Mass of KCl (g)}}{75 \ \text{mL}} \times 100 \).
Step 4: For part (b), calculate the mass of sucrose (C₁₂H₂₂O₁₁). Use the molar mass of sucrose (\( 12 \times 12.01 \ \text{g/mol} + 22 \times 1.008 \ \text{g/mol} + 11 \times 16.00 \ \text{g/mol} \)) to find the mass of 0.044 mol of sucrose: \( \text{Mass of sucrose} = \text{Moles of sucrose} \times \text{Molar Mass of sucrose} \).
Step 5: Substitute the calculated mass of sucrose and the given volume of solution (380 mL) into the mass/volume percent formula: \( \text{Mass/Volume Percent} = \frac{\text{Mass of sucrose (g)}}{380 \ \text{mL}} \times 100 \).

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Key Concepts

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

Mass/Volume Percent Concentration

Mass/volume percent concentration is a way to express the concentration of a solution, defined as the mass of solute (in grams) per 100 mL of solution. It is calculated using the formula: (mass of solute in grams / volume of solution in mL) × 100. This measurement is particularly useful in chemistry for understanding how concentrated a solution is.
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Percent Concentrations Concept 1

Molarity and Moles

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. To find the mass of a solute from its moles, one can use the molar mass, which is the mass of one mole of that substance. Understanding how to convert between moles and grams is essential for calculating mass/volume percent concentration.
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Dilution and Solution Preparation

Dilution refers to the process of reducing the concentration of a solute in a solution, typically by adding more solvent. When preparing solutions, it is important to know the final volume and the amount of solute needed to achieve the desired concentration. This concept is crucial for accurately calculating mass/volume percent concentrations in various scenarios.
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