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Chemistry 16.1
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Properties of Solutions >
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Solution Formation
Solution Formation
What factors determine the rate at which a substance dissolves?
16.1
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Properties of Solutions >Solution Formation
The compositions of the solvent and the solute determine whether a substance will dissolve. The factors that determine how fast a substance dissolves are
• stirring (agitation)
• temperature
• the surface area of the dissolving particles
16.1
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Properties of Solutions >Solution Formation
A cube of sugar in cold tea dissolves slowly.
16.1
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Properties of Solutions >Solution Formation
Granulated sugar dissolves in cold water more quickly than a sugar cube, especially with stirring.
16.1
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Properties of Solutions >Solution Formation
Granulated sugar dissolves very quickly in hot tea.
16.1
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Properties of Solutions >Solution Formation
Stirring and Solution Formation
Stirring speeds up the dissolving process because fresh solvent (the water in tea) is continually brought into contact with the surface of the solute (sugar).
16.1
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Properties of Solutions >Solution Formation
Temperature and Solution Formation
At higher temperatures, the kinetic energy of water molecules is greater than at lower temperatures, so they move faster. As a result, the solvent molecules collide with the surface of the sugar crystals more frequently and with more force.
16.1
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Properties of Solutions >Solution Formation
Particle Size and Solution Formation
A spoonful of granulated sugar dissolves more quickly than a sugar cube because the smaller particles in granulated sugar expose a much greater surface area to the colliding water molecules.
16.1
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Properties of Solutions >
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Solubility
Solubility
How is solubility usually expressed?
16.1
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Properties of Solutions >Solubility
A saturated solution contains the maximum amount of solute for a given quantity of solvent at a given temperature and pressure.
An unsaturated solution contains less solute than a saturated solution at a given temperature and pressure.
16.1
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Properties of Solutions >Solubility
In a saturated solution, the rate of dissolving equals the rate of crystallization, so the total amount of dissolved solute remains constant.
16.1
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Properties of Solutions >Solubility
The solubility of a substance is the amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure to produce a saturated solution.
Solubility is often expressed in grams of solute per 100 g of solvent.
16.1
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Properties of Solutions >Solubility
Some liquids combine in all proportions, while others don’t mix at all.
• Two liquids are miscible if they dissolve in each other in all proportions.
• Two liquids are immiscible if they are insoluble in each other.
16.1
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Properties of Solutions >Solubility
Oil and water are immiscible.
16.1
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Properties of Solutions >
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Factors Affecting Solubility
Factors Affecting Solubility
What conditions determine the amount of solute that will dissolve in a given solvent?
16.1
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Properties of Solutions >
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Factors Affecting Solubility
Temperature affects the solubility of solid, liquid, and gaseous solutes in a solvent; both temperature and pressure affect the solubility of gaseous solutes.
16.1
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Properties of Solutions >Factors Affecting Solubility
Temperature
• The solubility of most solid substances increases as the temperature of the solvent increases.
• The solubilities of most gases are greater in cold water than in hot.
16.1
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Properties of Solutions >Factors Affecting Solubility16.1
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Properties of Solutions >Factors Affecting Solubility
A supersaturated solution contains more solute than it can theoretically hold at a given temperature.
The crystallization of a supersaturated solution can be initiated if a very small crystal, called a seed crystal, of the solute is added.
16.1
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Properties of Solutions >Factors Affecting Solubility
A supersaturated solution is clear before a seed crystal is added.
16.1
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Properties of Solutions >Factors Affecting Solubility
Crystals begin to form in the solution immediately after the addition of a seed crystal.
16.1
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Properties of Solutions >Factors Affecting Solubility
Excess solute crystallizes rapidly.
16.1
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Properties of Solutions >Factors Affecting Solubility16.1
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Properties of Solutions >Factors Affecting Solubility
Pressure
Changes in pressure have little effect on the solubility of solids and liquids, but pressure strongly influences the solubility of gases.
Gas solubility increases as the partial pressure of the gas above the solution increases.
16.1
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16.1 Section Quiz.
1. For a given substance, which of the following will NOT influence how fast it dissolves?
a. temperature
b. amount of agitation
c. molar mass
d. size of the crystals
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16.1 Section Quiz.
2. The solubility of a substance is often expressed as the number of grams of solute per
a. 100 liters of solvent.
b. 1 cm3 of solvent.
c. 100 grams of solution.
d. 100 grams of solvent.
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16.1 Section Quiz.
3. The solubility of a gas in a solvent is affected by
a. both temperature and pressure.
b. only pressure.
c. only temperature.
d. both pressure and agitation.
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16.2Molarity
Molarity
How do you calculate the molarity of a solution?
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Molarity
a. The concentration of a solution is a measure of the amount of solute that is dissolved in a given quantity of solvent.
A dilute solution is one that contains a small amount of solute.
A concentrated solution contains a large amount of solute.
16.2
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Molarity
a.Molarity (M) is the number of moles of solute dissolved in one liter of solution.
b.To calculate the molarity of a solution, divide the moles of solute by the volume of the solution.
16.2
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Molarity
a. To make a 0.5-molar (0.5M) solution, first add 0.5 mol of solute to a 1-L volumetric flask half filled with distilled water.
16.2
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Molarity
a. Swirl the flask carefully to dissolve the solute.
16.2
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Molarity
a. Fill the flask with water exactly to the 1-L mark.
16.2
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16.2
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16.2
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16.2
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16.2
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Problem Solving 16.8 Solve Problem 8 with the help of an interactive guided tutorial.
for Sample Problem 16.2
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16.3
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Sample Problem 16.3
16.3
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Sample Problem 16.316.3
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Sample Problem 16.316.3
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for Sample Problem 16.3
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16.2Making Dilutions
Making Dilutions
What effect does dilution have on the total moles of solute in a solution?
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Making Dilutions
Diluting a solution reduces the number of moles of solute per unit volume, but the total number of moles of solute in solution does not change.
16.2
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Making Dilutions
a. The total number of moles of solute remains unchanged upon dilution, so you can write this equation.
a. M1 and V1 are the molarity and volume of the initial solution, and M2 and V2 are the molarity and volume of the diluted solution.
16.2
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Making Dilutions
a. Making a Dilute Solution
16.2
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Making Dilutions
a. To prepare 100 ml of 0.40M MgSO4 from a stock solution of 2.0M MgSO4, a student first measures 20 mL of the stock solution with a 20-mL pipet.
16.2
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Making Dilutions
a. She then transfers the 20 mL to a 100-mL volumetric flask.
16.2
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Making Dilutions
a. Finally she carefully adds water to the mark to make 100 mL of solution.
16.2
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Making Dilutions
a. Volume-Measuring Devices
16.2
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16.4
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16.4
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16.4
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16.4
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for Sample Problem 16.4
`
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Percent Solutions
Percent Solutions
What are two ways to express the percent concentration of a solution?
16.2
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Percent Solutions
The concentration of a solution in percent can be expressed in two ways: as the ratio of the volume of the solute to the volume of the solution or as the ratio of the mass of the solute to the mass of the solution.
16.2
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Percent Solutions
Concentration in Percent (Volume/Volume)
16.2
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Percent Solutions
a. Isopropyl alcohol (2-propanol) is sold as a 91% solution. This solution consist of 91 mL of isopropyl alcohol mixed with enough water to make 100 mL of solution.
16.2
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16.5
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16.5
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16.5
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16.5
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Practice Problems For Sample Problem 16.5
Problem-Solving 16.15 Solve Problem 15 with the help of an interactive guided tutorial.
for Sample Problem 16.5
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Percent Solutions
Concentration in Percent (Mass/Mass)
16.2
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16.2 Section Quiz.
16.2.
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16.2 Section Quiz.
1. To make a 1.00M aqueous solution of NaCl, 58.4 g of NaCl are dissolved in
a. 1.00 liter of water.
b. enough water to make 1.00 liter of solution
c. 1.00 kg of water.
d. 100 mL of water.
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16.2 Section Quiz.
2. What mass of sodium iodide (NaI) is contained in 250 mL of a 0.500M solution?
a. 150 g
b. 75.0 g
c. 18.7 g
d. 0.50 g
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16.2 Section Quiz.
3. Diluting a solution does NOT change which of the following?
a. concentration
b. volume
c. milliliters of solvent
d. moles of solute
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16.2 Section Quiz.
4. In a 2000 g solution of glucose that is labeled 5.0% (m/m), the mass of water is
a. 2000 g.
b. 100 g.
c. 1995 g.
d. 1900 g.