Textbook Question
The concentration of cholesterol (C27H46O) in blood is approximately 5.0 mM. How many grams of cholesterol are in 250 mL of blood?
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Ch.9 Solutions
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
Chapter 9, Problem 3
A solution is prepared by dissolving 12.5 g of KBr in 20 mL of water at 60 °C (see Figure 9.3). Is this solution saturated, unsaturated, or supersaturated? What will happen if the solution is cooled to 10 °C?
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Verified step by step guidance1
Step 1: Analyze the solubility graph provided. Locate the curve for KBr (potassium bromide). Note that the graph shows solubility in grams of solute per 100 grams of water at various temperatures.
Step 2: Convert the given quantities into comparable units. The problem states that 12.5 g of KBr is dissolved in 20 mL of water. Since 20 mL of water is approximately 20 g (assuming the density of water is 1 g/mL), calculate the solubility in grams of KBr per 100 g of water using the formula: \( \text{Solubility} = \frac{12.5}{20} \times 100 \).
Step 3: Compare the calculated solubility value to the solubility of KBr at 60 °C from the graph. If the calculated solubility is less than the value on the graph, the solution is unsaturated. If it matches the value, the solution is saturated. If it exceeds the value, the solution is supersaturated.
Step 4: Determine what happens when the solution is cooled to 10 °C. Use the graph to find the solubility of KBr at 10 °C. Compare this value to the amount of KBr already dissolved in the solution. If the dissolved amount exceeds the solubility at 10 °C, excess KBr will precipitate out of the solution.
Step 5: Summarize the findings. State whether the solution is saturated, unsaturated, or supersaturated at 60 °C, and describe the precipitation process that occurs when the solution is cooled to 10 °C.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Solubility
Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature. For KBr, solubility increases with temperature, meaning more KBr can dissolve in water at higher temperatures. Understanding solubility is crucial for determining whether a solution is saturated, unsaturated, or supersaturated.
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Solubility Rules
Saturated, Unsaturated, and Supersaturated Solutions
A saturated solution contains the maximum amount of solute that can dissolve at a given temperature, while an unsaturated solution can still dissolve more solute. A supersaturated solution contains more solute than is typically soluble at that temperature, often achieved by heating the solution and then cooling it carefully. Identifying the state of a solution is essential for predicting its behavior when conditions change.
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Effect of Temperature on Solubility
Temperature significantly affects the solubility of most solids in liquids; generally, solubility increases with temperature. In the case of KBr, the graph indicates that at 60 °C, a certain amount can dissolve, but if the solution is cooled to 10 °C, the solubility decreases, potentially leading to precipitation of KBr. This concept is vital for understanding the changes in solution behavior with temperature variations.
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Related Practice
Textbook Question
Classify the following liquid mixtures as heterogeneous or homogeneous. Further classify each homogeneous mixture as a solution or colloid.
c. Hand lotion
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Textbook Question
The maximum amounts of lead and copper allowed in drinking water are 0.015 mg/kg for lead and 1.3 mg/kg for copper. Express these values in parts per million, and tell the maximum amount of each (in grams) allowed in 100 g of water.
Textbook Question
Which of the following pairs of substances would you expect to form solutions?
a. CCl4 and water
b. Benzene (C6H6) and MgSO4
c. Hexane (C6H14) and heptane (C7H16)
d. Ethyl alcohol (C2H5OH) and heptanol (C7H15OH)
Textbook Question
At a total atmospheric pressure of 1.00 atm, the partial pressure of CO2 in air is approximately 4.0 × 10-4atm. Using the data in Problem 9.4, what is the solubility of CO2 in an open bottle of seltzer water at 20 °C?