# Review 129

Match the items on the left to the items on the right. Click on Answers below the table to reveal the answer.

 1. aqueous A. Polar solvents dissolve polar solutes. Nonpolar solvents dissolve nonpolar solutes. 2. tincture B. A colloidal dispersion of liquids in liquids. 3. emulsion C. A solution in which the solvent is alcohol. 4. like dissolves like D. A solution in which the solvent is water.

1. D, 2. C, 3. B, 4. A

Explain how a solution can be both dilute and saturated.

Dilute simply means that there is very little solute in relation to the solvent. Saturated means that the solution has all of the solute dissolved possible under those conditions. A solution can be saturated and dilute at the same time because the terms are totally independent of each other.

Why do we put antifreeze in car radiators in the summer as well as in the winter?

Not only does antifreeze, a solute, lower the freezing point of the solvent, it also raises the boiling point of the solvent. Consequently, antifreeze is needed in the summer to prevent the car’s coolant from boiling over.

What will happen when a crystal of solute is added to an unsaturated solution?

When a crystal of solute is added to an unsaturated solution the crystal will dissolve because the solution doesn’t contain all of the dissolved solute possible.

What will happen when a crystal of solute is added to a supersaturated solution?

When a crystal of solute is added to a supersaturated solution, the delicate supersaturated state is upset, and all of the excess solute will crystallize out of solution.

Using the graph above, answer the following questions:

1. What is the solubility of ammonium chloride at 40°C?

~46 g

2. If 54 g of NH4Cl are dissolved at 68°C, is the solution saturated or unsaturated?

unsaturated

3. If 54 g of NH4Cl are dissolved at 30°C, how many grams don’t dissolve?

52 g – 42 g = 12 g

Describe, in detail, how to make one liter of a 1 M NaCl solution.

1. One mole of NaCl (58.0 g) is to be massed.

2. Fill a one liter volumetric flask approximately half full of distilled water.

3. Add the 58.0 g of NaCl to the distilled water, stopper the flask, and agitate until the NaCl has dissolved.

4. Complete filling the volumetric flask with distilled water to the etched line on the neck of the flask.

5. Agitate the flask several times to ensure proper mixing.

What is the molarity of a solution that contains 15.0 g NaCl in 1.25 L of solution?

M = moles of solute/liters of solution
? mo NaCl = 15.0 g NaCl x 1 mol NaCl/58.0 g NaCl = 0.259 mol NaCl
M = 0.259 mol NaCl / 1.25 L = 0.207 M

A solution of HCl is 0.200 M. What mass of acid is dissolved in 250mL of solution?

M = moles of solute/liters of solution
0.200 M = mol solute/0.250 L
mol solute = 0.0500 mol HCl
? g HCl = 0.0500 mol HCl x 36.5 g HCl / 1 mol HCl = 1.83 g HCl

A solution of Na2CO3 contains 65.0 g of solute dissolved in water to make a 3.00 M solution. What is the volume of the solution, in liters?

mol Na2CO3 = 65.0 g Na2CO3 x 1 mol Na2CO3 / 106.0 g Na2CO3
mol Na2CO3 = 0.613 mol Na2CO3
M = moles of solute / liters of solution
3.00 M = 0.613 mol Na2CO3 / L solution
L solution = 0.204 L

Fill in the blanks then highlight the paragraph to reveal the answers.

A solution is a (1)homogeneous mixture of two or more substances. Every solution is composed of a (2) solute, which is normally present in the smaller amount and is the substance that is (3) dissolved, and a (4) solvent, which is normally present in the greater amount and is the substance that does the dissolving. A carbonated drink is an example of a (5) gaseous solute dissolved in a (6) liquid solvent; the final phase is that of a (7) liquid. Air is an example of a (8) gaseous solution. Liquids, such as antifreeze and water, which dissolve in one another are said to be (9) miscible, while liquids that do not dissolve in one another, such as salad oil and vinegar, are said to be (10) immiscible. Brass, a mixture of copper and zinc, is an example of a solid solution known as a(n) (11) alloy. Because the particles in a solution are so small (molecules, atoms, or (12) ions), filtration cannot be used to separate the components nor do the components settle upon standing.
(13)Suspensions contain particles too large to be true solutions, and upon standing, separate. They are actually (14) homogeneous mixtures that can be (15) separated by filtration. They also exhibit the (16)Tyndall effect which is the scattering of a beam of light. (17)Colloids also exhibit the Tyndall effect, but do not separate upon standing.
The rate of solution expresses how (18) quickly a solute dissolves in a solvent. Henry’s Law: The (19) mass of a gas dissolved in a given volume of liquid is (20) directly proportional to the pressure of the gas.
For most solutes to be dissolved in liquid solvents:
— as temperature increases the rate of solution (21) increases
— as surface area increases, the rate of solution (22) increases
— stirring or agitating the mixture (23) increases the rate of solution.
(24) Electrolytes are substances that conduct an electric current when dissolved. (25) Nonelectrolytes are substances that do not conduct an electric current when dissolved. A solution is (26) concentrated if it contains a relatively large amount of solute compared to the amount of solvent. A solution is (27) dilute if it contains a relatively small amount of solute. (28) Solubility is a measure of how much solute can dissolve in a given amount of solvent at a given temperature. (29) Colligative properties depend only on the concentration of the solution. These properties include vapor pressure (30) depression, freezing point (31) depression, and boiling point (32) elevation.
Normally, if the temperature is increased, the solubility of a solid solute (33) increases. (For gaseous solutes, however, increasing the temperature (34) decreases solubility.)

Word Bank (Some words may be used more than once)

 alloy colligative colloids concentrated decreases depression dilute directly dissolved electrolytes elevation gaseous homogeneous immiscible increases ions liquid mass miscible nonelectrolytes quickly separated solubility solute solvent suspensions Tyndall effect

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