Concentration units
What is the equation for molality
m = moles solute/kg solvent
(Also, molarity (M) = moles solute/L solution)
Describe what happens when a covalent substance dissolves.
One molecule of covalent substance is surrounded by solvent molecules
What is the equation for freezing point deperession?
Delta T = - i Kf m
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
Describe what happens when an ionic substance is dissolved.
One ion of the substance is surrounded by molecules of the solvent
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?
(NH4)3P
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
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)
If you have a saturated solution of a solid solute and you lower the temperature, what will happen?
Precipitate will form (lower solubility at lower temperature)
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
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
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
Does the solubility of a gas increase or decrease with increasing temperature/
decreases
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
A chemist makes a 1.76 m solution by mixing Na2S with 150.0 g of water. How many grams of Na2S were used?
There were 20.6 g of Na2S used
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 L
Which part of the water molecule has a partial negative charge?
oxygen (when ionic substances dissolve, the water orients itself so the oxygen side is closest to the positive ions)
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