Woodland Park

Name ______

Woodland Park

High School

Chemistry

Unit 9

Solutions

Chemistry Unit 9: Solutions

Assignment / Can Only be done in Class / Done?
Podcast 9.1 Polarity and Solvation
Demo: Bottle Waves / Could be done at home or school
Worksheet 9.1: Polarity and Solvation
Podcast 9.2 Electrolytes and the Nature of Solutions
Demo: Electrolytes / Yes
Worksheet 9.2: Electrolytes and the Nature of Solutions
Podcast 9.3 Properties of Solutions
Worksheet 9.3: Properties of Solutions
Demo: Solutions—Full Class / Yes
Podcast 9.4 Molarity
Worksheet 9.4: Molarity
Podcast 9.5 Dilutions
Lab: Dilution Lab / Yes
Podcast 9.6 Colligative Properties
Worksheet 9.6: Colligative Properties
Podcast 9.7: Solution Stoichiometry
Worksheet 9.7: Solution Stoichiometry
Lab: Gravimetric Analysis / Yes
Unit 9 Vocab
Unit 9 Exam

Unit 9 Vocab

Dipole

Polar molecule

Van der Waals forces

Dispersion forces

Dipole interactions

Hydrogen bonds

Surface tension

Surfactant

Aqueous solutions

Solvent

Solute

Salvation

Electrolytes

Nonelectrolytes

Weak electrolyte

Strong electrolyte

Efflorsce

Dessicant

Deliquescent

Suspensions

Tyndall effect

Brownian motion

Emulsions

Solubility

Saturated solution

Unsaturated

Miscible

Immiscible

Henry’s Law

Supersaturated solution

Concentration

Dilute solution

Concentrated solution

Molarity

Boiling point elevation

Freezing point depression

Lab: Bottle Waves—Could be done as a take-home-lab

Subject/Concept: Chemistry - Polar/Nonpolar liquids

Purpose: The purpose of this activity is to observe the effects of combining polar and nonpolar liquids.

Materials: • clear bottle with lid (16-20 oz size)

• water

• rubbing alcohol

• food coloring

• vegetable or mineral oil

• duct tape (or other strong tape)

Procedure:

1. Half fill the bottle with water.

2. Add 1/3 cup rubbing alcohol.

3. Add mineral to fill the bottle to the brim.

4. Add 4 drops of food coloring, one at a time.

5. Close the bottle with the lid and seal with tape.

6. Turn the bottle in various directions and observe the waves produced.

Questions:

1. In which liquid did the food coloring dissolve and why?

2. Why do the liquids not mix?

3. Why is the colorless liquid layer always on top?

For Credit:

To receive credit, your parent or guardian must write a short note confirming that you performed the experiment for them and explained the results to their satisfaction using the concept of polarity. Attach your note to the back of this sheet.

Solubility of Gases in a liquid

Solubility of Solids in Liquids

Take Home Lab

Parent/Student Experiment

Title: Dancing Raisins

Subject/Concepts: Chemistry - Solubility of Gases

Purpose: The purpose of this activity is to observe the buoyant effect of carbonation on raisins.

Materials: • 2 clear glass cups

•1 cold light colored soda (7-up, Sprite, Ginger Ale, etc)

• 1 warm room light colored soda (room temperature or left in the sun)

NOTE: Sodas must be opened at the start of the experiment and have plenty of carbonation.

• 20 raisins (approximately)

Procedure:

1. Pour the cold soda in one glass. Pour the warm soda into a second glass.

2. Add 10 raisins to each glass of soda and observe the “dance of the raisins.”

Questions:

1. In which glass do the raisins “dance” faster?

2. Explain your observations using your knowledge of the solubility of gaseous solutes in liquid solvents at various temperatures.

3. Why do the raisins float up from the bottom of the glass? Why do they sink again when they reach the top?

For Credit:

To receive credit, your parent or guardian must write a short note confirming that you performed the experiment for them and explained the results to their satisfaction using the concept of solubility of gases. Attach your note to the back of this sheet.

Dilutions Lab Name

1.  Dissolve approximately 2.0 grams of “K2Cr2O7” into either a 250 mL or 200 mL volumetric flask

2.  Determine the molarity of your solution.

3.  Using the technique of serial dilutions, make up the following molarities of solutions.

a.  0.00085 M

Show all calculations and put all data in a neat organized table.

You will then transfer your samples into a small test tube. Then take your sample to the teacher and he or she will test your sample to see if you have the “right” answer.

Procedure:

Sketch a series of pictures that illustrate what you did in this lab

Questions:

1.  If your goal is to make a 1.22 x 10-6 M solution why don’t you just make it from the solid?

2.  What would happen to your final molarity if you added too much water to the volumetric flask in any of the steps? Explain your answer.

3.  What would happen to your final molarity if one extra drop of the stock solution is transferred into the volumetric flask? Explain your answer.

4.  We want to make a 0.00034-M solution of sugar-water (C6H12O6). How would you go about this? You should have a step-by-step procedure and all calculations.

Gravimetric Analysis Lab: Chemistry

Problem

You are to react approximately 100 mL of 0.15 M calcium chloride with 85 mL or 0.10 M sodium carbonate. The reaction forms a precipitate, which you will collect via filtration.

1.  Write the balanced chemical equation for the reaction above

2.  Determine which product is the precipitate and label all states of matter in your chemical equation

3.  Pour both solutions into the flask.

4.  Mass the dry filter paper.

5.  Vacuum filtrate the precipitate. This may take several successive filtrations to get all of the precipitate.

6.  Dry all filter papers and record the mass

7.  Subtract out the mass of the filter papers to determine the mass of the ppt.

8.  While the filtration is going on, perform the following calculation

q  Use the molarities and the volumes to determine the mass of ppt that will form.

Data Table

Volume of calcium chloride
Volume of sodium carbonate
Molarity of calcium chloride
Molarity of sodium carbonate
Mass of filter paper 1
Mass of filter paper 1 after drying with the ppt.
Mass of ppt (from filter paper #1)
Mass of filter paper 2
Mass of filter paper 2 after drying with the ppt.
Mass of ppt (from filter paper #2)
Total mass of the ppt
Expected mass of the ppt (from calculations)
Percent Yield

Procedure

You will need to both explain your procedure and draw pictures that illustrate how you performed this experiment

Calculations

Show all necessary calculations and chemical equations that show how you predicted the amount of ppt that was formed. Also show the percentage yield for the precipitate.

Questions (answer in complete sentences)

1.  Comment on why your percentage yield is not 100%. If the number is greater than 100%, then explain why it is greater. If the number is less than 100%, then explain why it is less.

2.  Give two ways how you could have done this experiment better. (Be very specific)

Worksheet 9.1: Polarity

1)  Explain why water is polar.

2)  Describe the hydrogen bonding between molecules in water

3)  How is hydrogen bonding responsible for the high surfaced tension and low vapor pressure of water?

4)  What is a surfactant? How does it affect the surface tension of water?

5)  Explain why water has a relatively high boiling point and heat of vaporization.

6)  What is the difference between the structure of liquid water and the structure of ice? How does this explain why ice floats on water?

7)  What is the significance of the statement “like dissolves like”? What does “like” refer to?

8)  Which of the following substance dissolve in water? Explain your answer in terms of polarity.

a.  CH4

b.  KCl

c.  He

d.  MgSO4

e.  C6H12O6 (glucose—a sugar)

f.  NaHCO3

Worksheet 9.2: Electrolytes-Nature of Solutions

1)  Distinguish between electrolyte and a non-electrolyte. Distinguish between a weak electrolyte and a strong electrolyte. Give an example of each.

2)  Identify the solvent and the solute in vinegar, a dilute aqueous solution of acetic acid.

3)  Write a chemical equation showing how calcium chloride dissolves in water.

4)  What is the basis for distinguishing among solutions, colloids, and suspensions?

5)  Give an example of a solution, a colloid, and a suspension.

Worksheet 9.3: Properties of Solutions

1.  Why do the temperatures on the graph only go from 0º C to 100º C ?

2.  Which substance is most soluble at 60º C ?

3.  Which two substances have the same solubility at 80º C ?

4.  Which substance’s solubility changes the most from 0º C to 100º C ?

5.  Which substance’s solubility changes the least from 0º C to 100º C ?

6.  What is the solubility of potassium nitrate at 90º C ?

7.  At what temperature does potassium iodide have a solubility of 150 g/ 100 cm3 water ?

8.  You have a solution of sodium nitrate containing 140 g at 65º C. Is the solution saturated, unsaturated, or supersaturated ?

9.  You have a solution of potassium chlorate containing 4 g at 65º C. How many additional grams of solute must be added to it, to make the solution saturated ?

Worksheet 9.4 Molarity

1.  Calculate the molarity, M, of the following solutions:

a.  3.0 moles of NaCl are dissolved in 1 liter of solution.

b.  0.5 moles of MgF2 are dissolved in 2 liters of solution.

c.  3 moles of NaOH are dissolved in 0.25 liters of solution.

2.  How many liters of a 4.0 M CaCl2 solution would contain 2 moles of CaCl2?

aOH

3.  How many liters of a 0.5 M CaCl2 solution would contain 3.5 moles of CaCl2?

4.  How many liters of a 2.5 M CaCl2 solution would contain 1.0 mole of CaCl2?

5.  How many moles of KCl are there in 2 liters of a 3.0 M solution?

6.  What is the molarity, M, of a solution in which 116 grams of KF are dissolved in 2 liters of solution?

7.  How many grams of KF are in 2 liters of a 3.0 M solution of KF?

8.  How many grams of NH3 are dissolved in 85 mL of a 0.75 M solution?

Worksheet 9.5 Dilutions

1.  25 mL of 5.6 M HCl are placed in a volumetric flask. The flask is filled to 250 mL with water. What is the molarity of the new solution?

2.  5.6 mL of NaOH are added to a flask and the flask is filled with water to the 200 mL mark. The concentration of the new solution is found to be .098 M. What was the initial molarity of the solution before the dilution was completed?

3.  A chemist has 300 mL of a 2.5 M KCl solution. The solution is diluted by adding 1.2 L of water to the original volume. What is the [KCl] of the diluted solution?

4.  A chemist has 2 liters of a 3.2 M hydrochloric acid solution. If the solution is left out in the room and enough water evaporates so that there is only 1.2 liters of solution left, what is the final molarity of this concentrated acid?

5.  When a chemist adds 1.0 L of water to 3.0 liters of a 0.8 M HF solution, what is the new concentration of the total HF solution?

6.  How much water will a chemist need to add to 200 mL of a 3.3 M KCl solution if they want to make a 1.0 M solution of KCl?

Worksheet 9.6: Colligative Properties Worksheet

1.  Define each of the following vocabulary terms

·  colligative property

·  boiling point elevation

·  freezing point depression

·  Molality

2.  Explain why the boiling point is elevated and the freezing point is lowered in a solution.

Worksheet 9.7: Solution Stoichiometry

1)  How many grams of AgCl are produced when 40.0 mL of 0.25M AgNO3 is reacted with excess NaCl? The other product is NaNO3.

2)  In the following reaction with excess HCl, 45 mL of 0.100 M NaHCO3 produces how many liters of carbon dioxide at STP?

NaHCO3 + HCl ® NaCl + H2O + CO2

3)  Excess Zinc reacts with 1.0 L of 0.50M hydrochloric acid. How many liters of hydrogen gas are produced at 585 torr and 50°C?

4)  4.50 grams of lead II chromate is produced from the reaction of 100 mL of sodium chromate and 100 mL lead II nitrate. What is the initial molarity of the lead II nitrate?

5)  50.0 mL of 0.75M potassium iodide reacts with 50.0 mL of 0.75 M lead II nitrate. How many grams of precipitate are formed? (Note that this is both a solution stoichiometry problem and a limiting reactant problem)

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