Solutions

Vocabulary

100

solute

substance or substances dissolved in a solution

200

saturated solution

a solution in which the maximum amount of solute is dissolved

300

concentration

amount of substance in a defined volume

400

molarity formula and symbol

M, moles solute/liters solution

500

molality formula and symbol

m, moles solute to kg solvent

Conceptual

100

If you have a saturated solution with a solid solute, what do you need to do to temerature to form a precipitate?

lower temperature

200

The solubility of a gas in a given solution is decreasing.  If temperature is constant, what is happening to pressure?

It is decreasing

300

In water, which part of the molecule is + and which part is -?

Oxygen part is negative and hydrogen part is +

400

A chemist makes a 1.76 m solution by mixing Na2S with 150.0 g of water. How many grams of Na2S were used?

20.6 g of Na2S used

500

Barium sulfate is insoluble in water. If a solution of barium nitrate and water is mixed with a solution of sodium sulfate and water, what reaction will occur?

Ba(NO3)2 (aq) + Na2SO4 (aq) → BaSO4 (s) + 2NaNO3 (aq)

Freezing and Boiling temperature

100

What is i for MgCl2 , NaOH, and Mg(OH)2?

3, 2, 3

200

What is the freezing point of a solution made by mixing 150.0 g of KCl with 550.0 grams of water? (Kf is 1.86 °C/m for water.)

-13.6 °C

300

What is the boiling point of a solution made by mixing 150.0 g of KCl with 550.0 grams of water? (Kb is 0.512 °C/m for water.)

103.75 °C

400

Solutions are made from water and the following solutes: NaCl, SrCl2, Ba(NO3)2, (NH4)3P, C2H6O, and Na2SO4. If the molalities of the solutions are all the same, which will have the lowest freezing point?

The (NH4)3P solution will have the lowest freezing point

500

The boiling point of ethanol is 78.37 °C. If the boiling point of a solution of water and ethanol is 80.56 °C, what is the molality of the solution? (Kb for ethanol is 1.07 °C/m)

2.05 m

Solution problems

100

A solution is made by dissolving 15.0 g of AgNO3 in enough water to make 125.0 mL of solution. What is the concentration in moles/liter?

0.706 M

200

You want to make 500.0 mL of a 3.0 M solution of KCl. How many grams of KCl will you need?

110 g

300

A chemist wants to make Bi2S3 according to the following reaction:

2Bi(NO3)3 (aq) + 3K2S (aq) → Bi2S3 (s) + 6KNO3 (aq)

If the student uses 67.1 mL of a 2.9 M solution of K2S and an excess of Bi(NO3)3, how many grams of Bi2S3 will be formed?

32 g

400

A chemist wants to make 50.0 grams of hydrogen gas using the following reaction:

Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)

If she has an excess of Mg, what volume of a 4.12 M solution of HCl will she need to use?

12.0 liters

500

You make a solution by mixing 40.3 grams of MgCl2 with 750.0 grams of water. What is the molality of the solution?

0.564 m