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Chemistry

Name:__________________

Period: ____

Solutions

Packet 10

Day In Class Work

1 What is molarity

2 Creating a Molar solution

3 Molarity

4 Conductivity Lab

5 Molarity Practice

6 Concentration WS

7 Determine the Molarity of NaCl

8 Solutions

Outcomes Students will be able to define and apply the following terms: solution, solvent, solute, and

molarity.

Students will calculate the number of moles in a certain number of milliliters, given that a 1

molar solution has 1 mole in 1000ml.

Students will calculate the molarity of a solution when given the number of moles and liters.

Students will calculate the amount of grams needed to prepare a molarity solution.

Students will explain the process of creating a solution.

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PROPERTIES OF SOLUTIONS

A solution is a mixture of materials, one of which is usually a fluid. A fluid is a material that flows, such

as a liquid or a gas. The fluid of a solution is usually the solvent, the larger amount. The material other

than the solvent is the solute, the lesser amount. We say that we dissolve the solute into the solvent.

Some solutions are so common to us that we give them a unique name. A solution of water and sugar is

called syrup. A solution of sodium chloride (common table salt) in water is called brine. A sterilized

specific concentration (0.15 molar) of sodium chloride in water is called saline. A solution of carbon

dioxide in water is called seltzer, and a solution of ammonia gas in water is called ammonia water.

A solution is said to be dilute, unsaturated if there is less of the solute. The process of adding more

solvent to a solution or removing some of the solute is called diluting. A solution is said to be

concentrated, supersaturated if it has more solute. The process of adding more solute or removing some

of the solvent is called concentrating. The concentration of a solution is some measurement of how much

solute there is in the solution.

Molarity, M

The molar concentration or molarity, M, of a solution is used to indicate the number of moles of

solute per liter of solution:

Molarity M mol

L

(no.of moles solute)

(no. of liters of solution)

The molarity of a solution is often used as a conversion factor between moles of solute and volume of

solution: it is a “molar density”.

Stoichiometry of Reactions in Solution

Problems involving solutions are very similar to the chemical stoichiometry problems we have

discussed earlier. The only difference is that the moles of reactant or product may need to be calculated

from a solution volume using the molarity (M = mol/L) as a conversion factor between volume and moles.

Example: What is the molarity of a solution containing 21.0 g NaCl in 200 mL of solution?

grams/molar mass = moles moles / Liters = Molarity

21 g NaCl = 0.36 moles NaCl 0.36 mole NaCl = 1.80 M

58.4g NaCl 0.200 L

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Chemistry: Molarity of Solutions

Directions: Solve each of the following problems. Show your work and include units for full credit.

1. What mass of the following chemicals is needed to make the solutions indicated?

a. 1.0 liter of a 1.0 M mercury (II) chloride (HgCl2) solution

b. 2.0 liters of a 1.5 M sodium nitrate (NaNO3) solution

c. 5.0 liters of a 0.1 M Ca(OH)2 solution

d. 100 mL of a 0.5 M (NH4)3PO4 solution

2. Calculate the molarity of the following solutions.

a. 12 g of lithium hydroxide (LiOH) in 1.0 L of solution

b. 198 g of barium bromide (BaBr2) in 2.0 L of solution

c. 54 g of calcium sulfide (CaS) in 3.0 L of solution

3. Calculate the volume of each solution, in liters.

a. a 1.0 M solution containing 85 g of silver nitrate (AgNO3)

b. a 0.5 M solution containing 250 g of manganese (II) chloride (MnCl2)

c. a 0.4 M solution containing 290 g of aluminum nitrate (Al(NO3)3)

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4. How many grams of potassium chloride (KCl) are required to make 2.0 L of a 3.0 M solution?

5. How many grams of magnesium chloride (MgCl2) are needed to make 6.0 L of a 3.0 M solution?

6. What mass of barium chloride (BaCl2) is needed to make 0.5 L of a 4.0 M solution?

7. What mass of iron (II) sulfate (FeSO4) is needed to make 200 mL of a 0.25 M solution?

8. What is the molarity of a solution in which 1.6 g of sodium hydroxide (NaOH) are dissolved in 125 mL of

solution?

9. What is the molarity of a solution in which 5.0 g of sodium carbonate (Na2CO3) are dissolved in 200 mL of

solution?

10. How many grams of silver nitrate (AgNO3) are needed to make 2.0 L of a 0.10 M solution?

11. 2.0 L of a solution contain 25 g of potassium permanganate (KMnO4). What is the molarity of the solution?

12. How many grams of glycerine (C3H8O3) are needed to make 100 mL of a 2.5 M solution?

13. What is the molarity of a solution containing 150 g of zinc sulfate (ZnSO4) per liter?

14. A test tube contains 10 mL of a 3.0 M CaCO3 solution. Calculate the number of grams of CaCO3 in the tube.

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Creating a molar solution

To practice making solutions choose a slip of paper from the box on the teacher’s desk. The

solution which is written on the paper is the one to be prepared. The amount of solution to be prepared is

_________, the concentration of the solution is __________, and the solid to be used for preparing the

solution is __________.

Step 1: Calculate the amount of solid needed to create the solution. __________

T. I.

Step2: Measure the desired amount of solid and place it in a 250mL beaker.

Step 3: Dissolve the solid in distilled water. Use less water than the amount of solution that is to be

prepared. For example, if 250mL of solution is to be prepared only add 200mL of water to the beaker.

Step 4: Obtain the correct size volumetric flask from the table. Empty the

solution into the flask by using a funnel or stirring rod. Make sure all the solid is

transferred to the flask. Using a medicine dropper add distilled water to the flask

until the meniscus reaches the etched line on the flask’s neck.

T. I.

Step 5: Add the new solution created to the stock bottle in the middle of the room. Rinse out the

volumetric flask and place it on the table in the middle of the room.

Problems:

How many grams of beryllium chloride are needed to make 125 mL of a 0.050 M solution?

Explain how you would make 450 mL of a 0.250 M NaOH solution.

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Answer the following Molarity questions. Show all your work

1. Sea water contains roughly 28.0 g of NaCl per liter. What is the molarity of sodium chloride in sea

water?

2. What is the molarity of 245.0 g of H2SO4 dissolved in 1.00 L of solution?

3. What is the molarity of 5.30 g of Na2CO3 dissolved in 400.0 mL solution?

4. What is the molarity of 5.00 g of NaOH in 750.0 mL of solution?

5. How many moles of Na2CO3 are there in 10.0 L of 2.0 M soluton?

6. How many moles of Na2CO3 are in 10.0 mL of a 2.0 M solution?

7. How many moles of NaCl are contained in 100.0 mL of a 0.20 M solution?

8. What weight (in grams) of NaCl would be contained in problem 7?

9. What weight (in grams) of H2SO4 would be needed to make 750.0 mL of 2.00 M solution?

10. What volume (in mL) of 18.0 M H2SO4 is needed to contain 2.45 g H2SO4?

11. What volume (in mL) of 12.0 M HCl is needed to contain 3.00 moles of HCl?

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Conductivity of solutions Purpose: To investigate the ability of different solutions to conduct electricity.

Procedure:

1. Get a conductivity tester, a 9-volt battery, a towel, and 100mL beakers.

2. Go to one of the numbered lab stations.

3. Connect the battery to the conductivity tester. Touch the “electrodes” of the meter to a solid metal

object (such as a tap). The light on the meter will flash if the meter and battery are working properly.

4. Each lab station has a number. Place 20mL of the solution in the beaker.

5. Place the electrodes of the conductivity meter into the solution. Leave the electrodes in the solution for

only a few seconds (to reduce corrosion). Record your reading in the chart below:

6. Rinse the electrodes with tap water and wipe dry. Move to the next station.

7. Repeat steps 4-6 until you have tested all of the solutions.

8. Rinse and dry the electrodes. Disconnect the battery. Clean the lab station that you were at last. Return

all equipment.

Observations:

Station 1

Concentration

Station 2

% Ionic Character

Chemical Conductivity Chemical Conductivity

0.01M NaCl NaCl

0.07M NaCl LiCl

0.14M NaCl KCl

0.21M NaCl CaCl2

0.28M NaCl

Station 3

Number of Ions

Station 4

Drinks

Chemical Conductivity Drinks Conductivity

NaCl Gatorade

MgCl2 Lemonade

AlCl3 Water

Soda

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Questions :

1. Define electrolyte.

2. Electricity (i.e. a flow of electrons) does not pass through pure water. In order for electrons to move

through a solution they must be shuttled by ions. Thus, the solutions that conducted electricity contained

ions. List the ions that exist in each of these solutions: NaCl, MgCl2, KCl, and CaCl2.

3. Determine the % ionic character for the following compounds.

% ionic Conductivity

What type of relationship is there between % ionic

character and conductivity?

4. Determine how many grams of NaCl are needed to create the following solution in 1 liter of water.

Molarity = Moles / Liters moles = grams / molar mass

0.01M NaCl

0.07M NaCl

0.14M NaCl

0.21M NaCl

0.28M NaCl

5. Why is Gatorade a better electrolyte than water? Why is Gatorade more beneficial to an athlete than

water?

NaCl

LiCl

KCl

CaCl2

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Molarity Practice Worksheet

Find the molarity of the following solutions:

1) 0.5 moles of sodium chloride is dissolved to make 0.05 liters of solution.

2) 0.5 grams of sodium chloride is dissolved to make 0.05 liters of solution.

3) 0.5 grams of sodium chloride is dissolved to make 0.05 mL of solution.

4) 734 grams of lithium sulfate are dissolved to make 2500 mL of solution.

5) 6.7 x 10-2

grams of Pb(C2H3O2)4 are dissolved to make 3.5 mL of solution.

6) I have two solutions. In the first solution, 1.0 moles of sodium chloride is dissolved in tap water

to make 1.0 liters of solution. In the second one, 1.0 moles of sodium chloride is added to 1.0

liters of distilled water. Is the molarity of each solution the same? Explain your answer.

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Concentration Worksheet

1) How many grams of beryllium chloride are needed to make 125 mL of a 0.050 M solution?

2) How many grams of beryllium chloride would you need to add to 125 mL of water to make a 0.50

molar solution?

3) How many grams of magnesium chloride should be mixed with 225 mL of water to make a 0.5

molar solution.

4) Explain how to make at least one liter of a 1.25 molar ammonium hydroxide solution.

5) What is the molarity of a solution in which 0.45 grams of sodium nitrate are dissolved in 265 mL

of solution.

6) What is molarity of H3SO4 in a solution made by adding 3.4 grams of sulfuric acid to 3,500 mL of

water?

7) What will the volume of a 0.50 M solution be if it contains 25 grams of calcium hydroxide?

8) How many grams of ammonia are present in 5.0 L of a 0.050 M solution?

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Determine the molarity of an unknown solution of NaCl.

There are 4 sodium chloride solutions on the center table choose one solution and determine the molarity

of that solution.

Problem:

Procedure:

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Data and Calculations:

Discussion:

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Solutions

What is a solution?

What is the difference between solute and solvent?

Circle the solvent for each example:

50g of NaCl in 100ml water

10g of Kool-aid in 200 ml water

200g sugar in 100g of water

If a molar solution has 1 mole in 1000ml how many mole would there be in the following:

900ml = 750ml = 12ml = 5400ml =

What is molarity and the equation used to determine it?

1. How many grams of CuSO4 are needed to prepare 1 liter of a 4 Molar solution?

2. You have weighed out 0.786 gm of Fe(OH)3 and dissolved it in 500 ml of deionized water.

What is the Molarity?

3. Mr. Luke E. Zee wants to make 250 ml of a 0.5 M Hg(NO3)2 solution. How many grams

should he weigh out?

4. Calculate how many grams of MgCl2 would be needed to make 2 liters of a 0.5 M solution?

5. Mrs. C. Moore Hiney has weighed out 4.8777 grams of Ca(HCO3)2 and dissolved it in 100 ml

of deionized water. What is the molarity?

Explain the process for creating a 500ml Sodium Hydroxide, NaOH, solution that has a molarity of

0.10M.

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Molarity

1. Write the formula for molarity.

2. What are the units of molarity?

3. If 4 moles of Fe(OH)3 dissolved in 100 ml of deionized water,

A. What is the name of the compound?

B. What is the Molarity?

C. How many grams did you weigh out?

4. If you weigh out 54.32 grams of CaSO4 and dissolve it in 500 ml of DI water

A. What is the name of the compound?

B. How many moles have you weighed out?

C. What is the molarity?

5. You need to prepare 2 liters of a 0.25 M MgSO4 solution.

A. How many milliliters do you need to make?

B. How many grams of MgSO4 do you need to weigh out?

6. You need to prepare enough 0.23 M (NH3)3PO4 solution to run 40 tests. Each test requires about 10

milliliters.

A. What is the minimum volume you should prepare?

B. You decide to prepare 500 ml of solution in case of an accidental spill or a repeat. How many

grams of (NH3)3PO4 should you weigh out?

C. What is the molarity of the solution?

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Show all work

1. Determine the molarity of the solution containing 1.5 mol of NaOH in 1000 mL total volume of

solution.

2. Determine the molarity of the solution containing 0.4 mol of NaOH in 100 mL total volume of

solution.

3. Determine the molarity of the solution containing 1.5 mol of KNO3 in 250 mL total volume of

solution.

4. Determine the molarity of the solution containing 2.4 mol of KI in 140 mL total volume of

solution.

5. Determine the number of moles of NaOH in 500 mL of a 0.6 M NaOH solution.

6. Determine the number of moles of NaCl in 100 mL of a 1.2 M NaCl solution.

7. Determine the number of moles of FeSO4 in 200 mL of a 0.8 M FeSO4 solution.

8. Determine the number of moles of HI in 100 mL of a 1.2 M HI solution.

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9. What is the volume of 0.5 M NaI needed to have 0.25 mol NaI?

10. What is the volume of 5.0 M KBr needed to have 1.0 mol KBr?

11. How many grams of LiOH is needed to make 250 mL of a 0.33 M LiOH solution?

12. How many grams of Ca(NO2)2 is needed to make 800 mL of a 2.0 M Ca(NO2)2 solution?

13. How do you prepare 1.0 L of a 4.0 M KOH solution?

14. How do you prepare 250 mL of a 0.2 M NaI solution?

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Reactions in Aqueous Solution

Molarity

Solution Concentration

If 6.73 g of Na2CO3 is dissolved in enough water to make 250. mL of solution, what is the molarity

of the sodium carbonate? What are the molar concentrations of the Na+ and CO3

2 ions?

Some potassium dichromate (K2Cr2O7), 2.335 g, is dissolved in enough water to make exactly 500.

mL of solution. What is the molarity of the potassium dichromate? What are the molar

concentrations of the K+ and Cr2O7

2 ions?

What is the mass, in grams, of solute in 250. mL of a 0.0125 M solution of KMnO4?

What volume of 0.123 m NaOH, in milliliters, contains 25.0 g of NaOH?

If 4.00 mL of 0.0250 M CuSO4 is diluted to 10.0 mL with pure water, what is the molarity of

copper(II) sulfate in the diluted solution?

. For each solution, identify the ions that exist in aqueous solution & specify the concentration of

each.

a) 0.25 M (NH4)2SO4

b) 0.056 M HNO3

c) 0.123 M Na2CO3

d) 0.00124 M KClO4

Stoichiometry of Reactions in Solution

What volume of 0.125 M HNO3, in milliliters, is required to react completely with 1.30 g of

Ba(OH)2?

2 HNO3(aq) + Ba(OH)2(s) Ba(NO3)2(aq) + 2 H2O(l)

2 NaCl(aq) + 2 H2O(l) H2(g) + Cl2(g) + 2 NaOH(aq)

What mass of NaOH can be formed from 10.0 L of 0.15 M NaCl? What mass of chlorine can be

obtained?

2 NaCl(aq) + 2 H2O(l) H2(g) + Cl2(g) + 2 NaOH(aq)

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Molarity Lab – Murder Investigation

BACKGROUND: A crime has been committed and you, as the forensic detective, as going to use your

knowledge of solution chemistry to solve the crime. Miss Scarlet was found dead on the floor of the

ballroom. Beside her body police found a clear liquid, undoubtedly the murder weapon. Detectives were

quick to ascertain that the murder weapon was one of two chemicals. They knew that Miss Scarlet has a

violent allergic reaction to potassium iodide, and that there was widespread use of silver nitrate, which is

toxic if ingested, by several members of the household. Police further discovered the following evidence.

Professor Plum, an eccentric chemistry teacher, was working in the study with silver nitrate solutions of

molarities 0.20 to 0.30. Miss Scarlet was Plum's worst student, arriving to class late, being responsible for

lots of broken glassware, and rarely cleaning up after her experiments. The policeman in charge, never

having had a chemistry class, did not seriously consider this to be a motive for murder.

Mrs. White, an asthmatic, has a prescription for silver nitrate in the bathroom. Her pharmacist assures us

that her potassium iodide solution has a molarity in the range of 0.05 M to 0.10 M. That Mrs. White was

presently rooming with Miss Scarlet's ex-boyfriend led the police to suspect her. Neither she nor her

boyfriend could be found in the lounge for comment.

Mr. Green, a photographer, had solutions of silver nitrate between 0.11 M and 0.15 M in the darkroom.

Mr. Green apparently had been caught scarlet-handed at his own blackmail game. Pictures of him with

Miss Scarlet were found hidden in Scarlet's bedroom. Mrs. Green should be spared seeing the pictures if

at all possible.

Mrs. Peacock, wearing the same dress as Miss Scarlet, was found in the stable, administering silver

nitrate solution to her horse. When questioned, she admitted that her horse had a severe case of bronchitis.

Her veterinarian informed detectives that the strength of the solution was greater than 0.50 M. It is likely

that she knew of Miss Scarlet's violent allergy to potassium iodide, since they had been lab partners in

Professor Plum's chemistry class. Professor Plum recalled how angry Mrs. Peacock would get when Miss

Scarlet came late to class, unprepared for the experiments, and how she invariably got sick a few days

before the labs were due.

Colonel Mustard, had silver nitrate solutions of 0.31 M to 0.48, in the conservatory. The Colonel, who

despised the left-wing politics of Miss Scarlet, enjoyed his leisure hours making explosives. Colonel

Mustard had been the interim assistant principal at the high school and was largely responsible for closing

the campus when Miss Scarlet, then president of the student body, overthrew the administration and took

control of the school.

YOUR TASK: You can obtain a sample of the murder weapon found at Miss Scarlet's side by asking

your teacher for it, in the classroom. If you can determine the molarity of the unknown solution, then you

can solve the case.

How can you determine the morality of an unknown solution?

Who was the murderer? What was the murder weapon? What was its molarity?