Topic 1

Determine the freezing point of a 0.51 molal solution of benzoic acid in chloroform. Chloroform has a freezing point of -63.5°C and a freezing point depression constant of 4.70°C•kg/mol. What is the freezing point of this solution? Determine the boiling point of a solution made by dissolving 0.60 mol K2SO4 in 1.0 kg water. Water has a boiling point elevation constant of 0.51°C•kg/mol. What is the boiling point of this solution?

-65.9°C 100.31°C

A 150 mL sample of hydrochloric acid (HCl) completely reacted with 60.0 mL of a 0.100 M NaOH solution. The equation for the reaction is given below. HCl + NaOH mc011-1.jpg NaCl + H2O What was the original concentration of the HCl solution?

0.040 M

The molar mass of KCl is 74.55 g/mol. If 8.45 g KCl are dissolved in 0.750 L of solution, what is the molarity of the solution?

0.151 M

A set of four 15.0-mL solutions—each in a similar open dish—was left at room temperature, and the amount that remained was recorded after every hour. Which of the solutions do you expect to be the first to completely evaporate from the open dish?

0.25 m Na2SO4

A chemistry teacher adds 50.0 mL of 1.50 M H2SO4 solution to 200 mL of water. What is the concentration of the final solution?

0.300 M

A stock solution is made by dissolving 66.05 g of (NH4)2SO4 in enough water to make 250 mL of solution. A 10.0 mL sample of this solution is then diluted to 50.0 mL. Given that the molar mass of (NH4)2SO4 is 132.1 g/mol, what is the concentration of the new solution?

0.400 M

A student was comparing the solubility of equal amounts of table salt and table sugar at different temperatures.The table below shows the four samples that the student used and the temperature of the water that they were dissolved in. Which of the samples most likely had the highest solubility?

1

A solution contains 6.21 g of ethylene glycol dissolved in 25.0 g of water. If water has a boiling point elevation constant of 0.512°C•kg/mol, what is the boiling point of the solution? (molar mass of ethylene glycol = 62.1 g/mol; boiling point of pure water = 100.00°C)

102.05°C

Which solution is the most concentrated?

2.0 mL of 10.5 M H2O2, where H2O2 has a molar mass of 34 g/mol

In a group assignment, students are required to fill 10 beakers with 0.720 M CaCl2. If the molar mass of CaCl2 is 110.98 g/mol and each beaker must have 250. mL of solution, what mass of CaCl2 would be used?

200 g

How many grams of NaCl will be needed to form 600 mL of a saturated solution at 100°C?

240 g

A chemist dilutes a 1.0 mL sample of 2.0 M KNO3 by adding water to it. If the concentration of the solution that is obtained is 0.0080 M, what is its volume?

250 mL

Rank these five scenarios from lowest freezing point (1) to highest freezing point (5). Each solution was made using 1.0 kg water as the solvent and the indicated number of moles of each solute. 0.5 mol NaCl 1.0 mol K3PO4 2.0 mol glucose 1.5 mol ethylene glycol 0.8 mol MgCl2

5 1 3 4 2

Given that the molar mass of NaNO3 is 85.00 g/mol, what mass of NaNO3 is needed to make 4.50 L of a 1.50 M NaNO3 solution?

574 g

A student prepares 150.0 mL of 1.40 M HCl using 35.0 mL of a stock solution. What is the concentration of the stock solution?

6.00 M

In a school's laboratory, students require 50.0 mL of 2.50 M H2SO4 for an experiment, but the only available stock solution of the acid has a concentration of 18.0 M. What volume of the stock solution would they use to make the required solution?

6.94 mL

The graph below shows how solubility changes with temperature. mc022-1.jpg What is the solubility of Na2HAsO4 at 60°C?

65 g/100 mL of water

Which graph correctly shows the effect on the freezing point caused by increasing the molality of a solution ?

A

A sugar solution containing 0.84 mol sugar has a concentration of 1.20 m. How many kilograms of water must the solution contain? Use mc027-1.jpg.

A 0.70 kg

How many liters of water must be added to 0.291 g of NaCl to create a saltwater solution that has a concentration of 2.41 g/L? Use mc010-1.jpg.

A. 0.121 L

Juanita dissolves 46 g of MgBr2 (molar mass: 184.11 g/mol) in 0.5 kg of distilled water. What is the molality of the solution? Use mc004-1.jpg.

A. 0.5 m

A solution of sulfuric acid has a concentration of 0.0980 g/L. If the density of the acid is 1.84 g/mL, what is the concentration in ppm? Use mc020-1.jpg.

A. 53.3 ppm

An aqueous solution is made from a molecular compound rather than from an ionic compound. If some ions are present in solution, which best describes the solute?

A. A weak electrolyte.

In which process do ionic compounds separate into their oppositely charged constituent ions when they are dissolved in water?

A. Dissociation

Which substance will most likely ionize when it is dissolved in water?

A. HBr

Which statement best describes the process of making a solution by diluting a stock solution?

Add more solvent to decrease the concentration.

During a lesson in physical science about changes of matter, students made ice cream. Among the materials that are required to make ice cream is salt. Which answer choice best explains the role of salt in this activity?

Adding salt to ice lowers the freezing temperature. This helps the milk mixture to freeze sooner because the mixture will reach the freezing temperature sooner.

A group of students is in the laboratory performing an experiment on the effect of adding salt to water. Which observation are students likely to make as they increase the molality of the saltwater solution?

As the molality increases by 1 m, there is a corresponding decrease of 1.86°C in the solution's freezing point.

Use the table to compare the solubilities of substances. Check all of the boxes that apply.

Aspirin is less soluble than table salt, but more soluble than carbon dioxide. A saturated solution of table sugar is more concentrated than a saturated solution of table salt.

`A glucose solution that is prepared for a patient should have a concentration of 180 g/L. A nurse has 18 g of glucose. How many liters of water should she add to the glucose to obtain the required solution? Use mc011-1.jpg.

B. 0.10 L

A solution is made by dissolving 373.5 g of Pb(NO3)2 (molar mass: 331.2 g/mol) in 2.00 × 103 g of water. What is the molality of the solution? Use mc005-1.jpg.

B. 0.564 m

How many liters of water must be added to 5.40 g of sodium nitrate to create a solution that has a concentration of 3.81 g/L? Use mc030-1.jpg.

B. 1.42 L

A researcher dilutes 30.0 mL of ethanol to 300.0 mL with distilled water. What is the percentage concentration by volume of the resulting solution? Use mc031-1.jpg.

B. 10.0%

Calculate the molality of a solution that was made by dissolving 4.9 g of H2SO4 in 50 g of water. Use mc002-1.jpg.

B. 1m

Ethanol is used widely as a solvent in laboratories for various chemical reactions. A laboratory technician takes 50.0 mL of ethanol and dilutes it to 100.0 mL with distilled water. What is the percentage concentration by volume of the resulting solution? Use mc015-1.jpg.

B. 50.0%

Which substance is a strong electrolyte?

B. Ba(OH)2

Which is a characteristic of a weak electrolyte?

B. It partially dissociates or ionizes in water.

Nonelectrolytes fail to ionize or dissociate in water because

B. They are very strongly bonded to each other.

Shown below is an ion from a salt molecule. Which statement best explains the event?

B. This is hydration, which occurs during dissociation.

Which chemical reaction involves the production of a gas?

B. Zn(s) + 2HCl(aq) -> H2(g) + ZnCl2(aq)

Calculate the molality of a solution that is made up of 250 g of water and 20.0 g of NaOH. Use mc001-1.jpg.

C. 2.0 m

The concentration of 150.0 mL of Na2CO3 is found to be 30.0 ppm. What mass of Na2CO3 is dissolved in the solution if the density of the solution is 0.750 g/mL? Use mc022-1.jpg.

C. 3.38 x 10-3g

Consider the equation below. AgNO3(aq) + NaCl(aq) mc007-1.jpg AgCl(s) + NaNO3(aq) Which compound is the precipitate in this chemical reaction?

C. AgCl

Which of the following is a nonelectrolyte?

C6H12O6

Which of the following does not involve colligative properties?

Calcium silicide is added to liquid steel to increase the steel's ability to freeze.

Given that the density of water is 0.975 g/mL and that 171 g of sucrose (molar mass: 342.30 g/mol) is dissolved in 512.85 mL of water at 80°C, what is the molality of this solution? Use mc008-1.jpg.

D. 1.00 m

A solution is made by dissolving 0.611 mol of NaCl in 250 g of water. If the molar mass of NaCl is 58.44 g/mol, what is the molality of the solution? Use mc006-1.jpg.

D. 2.4 m

Which reaction would produce a solution that conducts electricity extremely well?

D. Ca(NO3)2(s) -> Ca2+(aq) + 2NO3-(aq)

Which is an example of dissociation?

D. Ca3(PO4)2 -> 3Ca2+ + 2PO43-

A doctor orders a blood sample from a child to test for traces of lead in the blood. Which of the following concentration units would best meet this need?

D. Parts per million

Which formula represents a double displacement reaction?

D. Pb(NO3)2(aq) + 2HCl(aq) -> 2HNO3(aq) + PbCl2(s)

For an experiment, a student needs a compound that has the following properties. • It dissolves in water. • It is an electrolyte. • It is excellent conductor of electricity. Which substance would be the best choice for the experiment?

D. Potassium chloride

Consider the reaction below. Zn(s) + 2HCl(aq) mc029-1.jpg H2(g) + ZnCl2(aq) Which product is a substance that is dissolved in solution?

D. ZnCl2

Which describes a precipitate in a chemical reaction?

D.A solid product formed from aqueous reactants.

Which statement about electrolytes and nonelectrolytes is not true?

Electrolytes disperse as molecules in a solution.

A student placed equal volumes of honey and of water in two, identical, open dishes, and left them at room temperature for 8 hours. She observed that the amount of water decreased, but the amount of honey seemed unchanged. Knowing that honey is a highly concentrated solution of sugar in water, which statement should the student make to explain this phenomenon?

Honey has a much lower vapor pressure than pure water has. So, pure water evaporates at a much higher rate.

Which is true about the dissolving process in water?

Molecules or ions of a solute spread throughout the water molecules.

If you make a solution by dissolving 1.0 mol of FeCl3 into 1.0 kg of water, how would the osmotic pressure of this solution compare with the osmotic pressure of a solution that is made from 1.0 mol of glucose in 1.0 kg of water?

NOT twice as large four times as large

Pellets of calcium chloride are spread on a sidewalk covered in water that is 36°C. Under which circumstance will the calcium chloride dissolve faster?

People walking on the sidewalk crush the calcium chloride pellets.

A student lives in a place that receives lots of snow and ice during the winter. The student has observed that the highway department spreads salt on the road after a snowfall. Which of the following correctly explains why the highway department uses salt on the roads?

Salt lowers the freezing point of water, which makes the melted snow on the road less likely to form ice.

How are the boiling point and freezing point of a solvent affected when a solute is added?

The boiling point increases, and the freezing point decreases.

Water is added to liquid isopropanol (a polar liquid) to form a solution of rubbing alcohol. Describe what happens on the molecular level as the water dissolves in the isopropanol. Which did you include in your response? Check all of the boxes that apply.

The isopropanol molecules are attracted to water's molecules at the surface of the particles. The isopropanol molecules then surround the water molecules and then are carried into the solution. The water molecules dissolve in a "like" isopropanol. The polar isopropanol molecules are attracted to the polar water molecules at the surface of the water. The isopropanol molecules surround the water molecules. The water molecules are carried into the solution. The water molecules spread evenly throughout the solution.

Consider two solutions made using water as the solvent: 1.0 m CaCl2 and 3.0 m sucrose. Describe how the osmotic pressures of these two solutions compare. Explain why this is true.

The osmotic pressures are the same because they both have the same amount of dissolved particles

Which is true about dissolving a polar substance in water?

The solute particles are carried into the solution.

The solubility of glucose at 30°C is 125 g/100 g water. Classify a solution made by adding 550 g of glucose to 400 mL of water at 30°C. Explain your classification, and describe how you could increase the amount of glucose in the solution without adding more glucose. Which did you include in your response? Check all of the boxes that apply.

The solution is supersaturated because for 400 mL of water, you should add 500 g of water. The solution is saturated. At 30°C, 500 g of glucose will dissolve in 400 mL of solution.

Which is the second step in the dissolving process?

The solvent molecules surround the solute particles.

A student stirs 2 tablespoons of honey into a glass of water. How will the addition of honey affect the water's colligative properties?

The water's osmotic pressure will increase, and its vapor pressure will decrea

Which statement accurately describes part of the dissolving process of a polar solute in water?

Water molecules surround solute molecules.

Which would be the best way to represent the concentration of a 1.75 M K2CrO4 solution?

[K2CrO4]

Brownian motion is not observed in a mixture that includes two phases. Which best identifies the mixture?

a suspension

The solubility of Solute D _______ as temperature increases. The solubility of Solute __ increases the most as temperature increases. The solubility of Solutes C and D is the same at __°C. As the temperature increases from 0 to 100, the solubility only changes by about __ grams for Solute B.

decreases E 20° 5

Which is an example of a nonaqueous solution?

gasoline

Under which conditions would the solubility of a gas be greatest?

high pressure and low temperature

Which method would increase the solubility of a gas?

increasing the pressure

Which of these factors will cause a solid solute to dissolve faster?

increasing the surface area of solute

A chemist dissolved crystals of an unknown substance into water at room temperature. He found that 33 g of the substance can be dissolved into 100 mL of water. What property of the unknown substance was the chemist most likely investigating?

its solubility

A solution contains 90 mL of methanol, 18 mL of propanol, and 2 mL of diethyl ether. Which is the solvent in this solution?

methanol

Which best defines concentration?

ratio that describes the amount of solute divided by the amount of solvent or solution

If the temperatures were raised slowly under the same conditions, would ice made from fresh water or sea water melt first? Which would boil first? Which of these would allow the temperature of an ice cream maker to drop below 0°C? Which requires colder temperatures to freeze, unsalted roads or salted roads? Which requires more heat to boil, pure water or a sugar solution used for making candy?

sea water fresh water salt + ice salted roads sugar solution used for making candy

Josh prepares a solution by mixing sodium nitrate and water. To calculate the molarity of the solution, Josh should calculate the moles of which substance, and why?

sodium nitrate, because it is the solute

The concentration of a solute in a solution is greater than the maximum concentration that is predicted from the solute's solubility. What is the best way to describe this solution?

supersaturated

Which factor influences both solubility and the rate of dissolution?

temperature

The osmotic pressure of a solution increases as

the number of particles of solute in the solution increases.

How would the vapor pressure of a solution that contains 0.5 mol of CaCl2 in 1.0 kg of water compare with the vapor pressure of a solution that contains 1.5 mol of glucose in 1.0 kg of water?

the same

Solute crystals are added to a solution until they begin to sink to the bottom of their container. The solution is then heated, and many more solute crystals dissolve. Which term best describes the solution immediately after it was heated?

unsaturated

A can of soda contains many ingredients, including vanilla, caffeine, sugar, and water. Which ingredient is the solvent?

water