Textbook Question
Which of the following solutions is more concentrated? (a) 0.500 M KCl or 0.500 mass % KCl in water
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Ch.13 - Solutions & Their Properties
Chapter 13, Problem 66
What is the mass percent concentration of the following solutions? (a) Dissolve 0.655 mol of citric acid, C6H8O7, in 1.00 kg of water. (b) Dissolve 0.135 mg of KBr in 5.00 mL of water. (c) Dissolve 5.50 g of aspirin, C9H8O4, in 145 g of dichloromethane, CH2Cl2.
Verified step by step guidance1
Step 1: Understand the concept of mass percent concentration, which is defined as the mass of solute divided by the total mass of the solution, multiplied by 100%. The formula is: \( \text{Mass percent} = \left( \frac{\text{mass of solute}}{\text{mass of solute} + \text{mass of solvent}} \right) \times 100\% \).
Step 2: For part (a), calculate the mass of citric acid using its molar mass. The molar mass of citric acid (C6H8O7) is calculated by adding the atomic masses of its constituent atoms: \( 6 \times 12.01 + 8 \times 1.01 + 7 \times 16.00 \). Multiply the molar mass by the number of moles (0.655 mol) to find the mass of citric acid.
Step 3: For part (a), add the mass of citric acid to the mass of water (1.00 kg or 1000 g) to find the total mass of the solution. Use the mass percent formula to calculate the mass percent concentration.
Step 4: For part (b), convert the mass of KBr from milligrams to grams (1 mg = 0.001 g). Add this mass to the mass of water (5.00 mL of water is approximately 5.00 g, assuming the density of water is 1 g/mL) to find the total mass of the solution. Use the mass percent formula to calculate the mass percent concentration.
Step 5: For part (c), add the mass of aspirin (5.50 g) to the mass of dichloromethane (145 g) to find the total mass of the solution. Use the mass percent formula to calculate the mass percent concentration.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mass Percent Concentration
Mass percent concentration is a way to express the concentration of a solute in a solution, calculated as the mass of the solute divided by the total mass of the solution, multiplied by 100. This measurement provides a clear understanding of how much solute is present relative to the total mass, which is essential for comparing concentrations in different solutions.
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00:38
Mass Percent Calculation
Molar Mass
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is crucial for converting between moles and grams when calculating concentrations, as it allows for the determination of how much solute is present in a given mass of solution, facilitating the calculation of mass percent concentration.
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Solution Preparation
Solution preparation involves dissolving a solute in a solvent to create a homogeneous mixture. Understanding the amounts of solute and solvent used is vital for accurately calculating concentrations, as the final concentration depends on both the mass of the solute and the total volume or mass of the solution.
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Related Practice
Textbook Question
Which of the following solutions has the higher molarity? (a) 10 ppm KI in water or 10,000 ppb KBr in water
Textbook Question
The ozone layer in the Earth's stratosphere has an average total pressure of 10 mm Hg 11.3 * 10-2 atm2. The partial pressure of ozone in the layer is about 1.2 * 10-6 mm Hg11.6 * 10-9 atm2. What is the concentration of ozone inparts per million, assuming that the average molar mass ofair is 29 g/mol?