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Unit 9 Solutions and thermochemistry Student Handout
Anticipation Guide
1) A solution can be made of not only liquids but gases as well and looks homogeneous.
Agree ______
Disagree ______
Why?
2) Orange juice cartons that say “made from concentrate” are better because they are made from pure orange
juice with no additional water.
Agree ______
Disagree ______
Why?
Questions/Main Ideas
Objective1: Describe what a solution is and what allows a solute to dissolve in a solvent
What Is a Solution?
1) Suspension
2)Aqueous Solution
3) Colloid
What is a Solution continued…
Components of a solution
Dissolving process
• When you add the solute to a solvent, the solute dissolves as it makes contact with
the solvent
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Solubility
Concentration
Key Questions
Answer the following questions about a 12M sugar water solution.
1) What kind of solution is it?
2) What is the solute?
3) What is the solvent?
4) What is the concentration?
CER 1 Determine if you agree or disagree with the statement below and provide at least 2 pieces of
evidence and your reasoning to support your view.
Mayonnaise is an example of a Colloid that has eggs as one of the solutes and oil as the solvent
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1) Oil and water do not mix because water repels oil.
Agree ______
Disagree ______
Why?
2) Soap is able to remove dirt from your hands because it is nonpolar like dirt is.
Agree ______
Disagree ______Why?
Questions/Main Ideas
Objective: Learn how to describe a solution and how to make a solution.
Concentrations of a solution
1) concentrated
2) dilute
3) saturated
4) unsaturated
5) supersaturated
Water: The universal solvent
Solubility and Liquids
Wax does not repel water
Ionic solids
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Detergents
Key Questions:
30 mL of salt solution is added to 100 mL of water.
A) What is the solvent?
1) salt solution 2) water
3) both
B) What is the solute?
1) salt solution 2) water
3) neither
C) What ions are present in the salt solution?
1) Na+
2) Cl−
3) both
D) The following figure represents soap.
Which end of the anion is hydrophobic? left end, right end
E) How will the anions on the surface of a beaker of water prefer to arrange themselves: A, B, C
F) How does soap interact with grease (see below)? A, B
CER 2 Determine if you agree or disagree with the statement below and provide at least 2 pieces of
evidence and your reasoning to support your view
NH3 is not able to dissolve in water because NH3 has a lone pair of electrons around the nitrogen
that makes in nonpolar and thus unable to dissolve in water.
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Questions/Main Ideas
Objective: Learn what solutions conduct electricity and how to calculate concentration.
Aqueous solutions
Electrolytes
Weak electrolytes
Nonelectrolytes
Concentration of solutions
• there are 4 different ways of calculating concentration
• for all calculations set up following table with info given and plug in relevant
values
Species
Grams
Moles
kg
Solute
Solvent
Total
1) Molarity
- moles of solute per liter of solution
M= moles solute
Liters solution
Ex. A solution is prepared by dissolving 25.0 g of MgCl 2 in enough water to make 450 mL
of solution. Calculate the molarity.
2) Mass percent
- percent by mass of solute in solution
- is value between 0 and 100
Mass %= mass solute
x 100
Mass solution
Ex. Calculate the mass percent of ethanol (CH3CH2OH) in an ethanol- water solution if 25.0
g of ethanol are
dissolved in 125 g of water.
Species
Solute
Solvent
Total
Grams
Moles
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kg
3) Parts per million (ppm)
-used for very dilute solutions and often used to show the amount of contaminants in a
sample of water
• Calculation similar to mass percent
• Ppm= mass solute
X 106
mass of solution
Ex. Calculate how many ppm of ethanol you have in the water solution from the previous
question
4) Molality
-moles solute per kg solvent
-m= number of moles of solute
kg solvent
Calculate molality of ethanol given in last problem
Key Question:A solution is prepared by mixing 85.0g of hexane, C6H14 and 45.0g of
decane, C10H22.
Species
Solute
Solvent
Total
Grams
Moles
1) Calculate the molality.
Calculate the mass percent of decane.
kg
2) Calculate the ppm of decane
CER 3 Determine if you agree or disagree with the statement below and provide at least 2 pieces of
evidence and your reasoning to support your view. When 20g of NaOH dissolves in 1000 g of water
creates a 0.50m solution that conducts electricity very well.
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3)
Anticipation Guide
1) If you want a solid to dissolve faster you can either heat the mixture, mix it or break the solid into smaller
pieces.
Agree ______
Disagree ______
Why?
2) Cooks add salt into hot water when making pasta only because it makes the pasta taste better.
Agree ______
Disagree ______
Why?
3) It will be harder to freeze Kool Aid into ice cubes than regular water.
Agree ______
Disagree ______Why?
Questions/Main Ideas
Objective: Predict the effect of changing physical condition on dissolving and the impact of
a solute on the boiling point and freezing point.
Effect of Temperature
Effect of pressure
Effect of surface area
Freezing point depression
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Boiling point elevation
Number of particles and fp and bp
What causes boiling?
Vapor Pressure
• Pressure created by every liquid as a result of the liquid evaporating
• The higher the vapor pressure the faster boiling can occur
Key Questions
A) Determine which of the following would produce a lower freezing point
1) C6H12O6
2) MgCl2
3) AlCl3
B) Which of the following would have a higher boiling point
1) C6H12O6
2) MgCl2
3) AlCl3
C. Why does warm soda taste so different than cold soda?
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CER 4 Determine if you agree or disagree with the statement below and provide at least 2 pieces of evidence and
your reasoning to support your view. Two friends decide to do an experiment to see what effect atmospheric pressure
has on water boiling. One goes to big bear mountain and the other stays here in the neighborhood. They
simultaneously start boiling water but the friend in the neighborhood really wants to win so he decides to add salt to
his water and claims his boiled faster. He argues this is because atmospheric pressure is lower here which is why his
boiled faster.
Questions/Main Ideas
Objective: Calculate the change in freezing point and boiling point as a result of adding a
solute to a solvent
Boiling Point Elevation
Freezing Point Depression
Boiling Point Elevation and Freezing Point Depression
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Ex. What are the freezing and boiling points of
naphthalene when 10.0g of nicotine, C10H14N2, is
dissolved in 50.0g of naphthalene?
Kf= 6.94 ˚C/m
kb= 6.2 ˚C/m
Freezing point= 80.29˚C Boiling point= 217.96˚C
Grams
Moles
nicotine
10g
0.06
Naphthalene
50g
Total
60g
kg
0.010kg
0.050kg
0.060kg
Question: Calculate the freezing point depression in a 0.0100 m aqueous solution of
MgSO4 with a kf= 1.86ºC/m
CER 5 Determine if you agree or disagree with the statement below and provide at least 2 pieces of evidence and
your reasoning to support your view. The boiling point of 80g of NaOH dissolved in 1000g of water is 107.44°C and
the freezing point is -2°C.
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1) When an object feels cold it is because“coldness” is traveling to your hand from the object.
Agree_____ Disagree______
Why?_____
2) Heat and temperature are the same thing
Agree_____ Disagree______
Why?_____
3) It is easier to burn your tongue eating a hot piece of toast then eating a hot bowl of soup.
Agree_____ Disagree______
Why?_____
4) A piece of ice melts because it absorbs heat from the surroundings.
Agree_____ Disagree______
Why?_____
Questions/Main Ideas
Objective Explain how energy can be measured and transferred in a solution and how
How is energy and
temperature related?
objects absorb heat differently.
Energy
• is the capacity to do work or supply heat
PE(Potential energy)
Heat vs. Temperature
Temperature Measurements
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KE(kinetic energy)
Units of Energy
• Measured in calories
• A calorie is defined as
The amount of heat energy needed to raise the temperature of one gram of
water one degree Celsius.
A) When you touch an object and it burns you, which direction does the
heat flow?
1) From object to hand
2) from hand to object
B) You put ice on your knee because of some soreness. Which direction is
heat flowing?
1) From knee
2) from ice
3) Heat not flowing
C) If a thermometer shows that the temperature is increasing, than the
liquid inside the thermometer is
1) Expanding
2) contracting
3) doing nothing
Heat capacity
• is the amount of heat it takes to change an object’s temperature by
exactly 1 Celsius
• Basically depends on what the substance is and how much of it you
have
Specific heat Capacity
• is the amount of heat it takes to change the temperature of 1 g of
substance 1 Celsius
• Basically depends only on the identity of the substance and is a
constant
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CER 6 Determine if you agree or disagree with the statement below and provide at least 2 pieces of
evidence and your reasoning to support your view.A 10. g cube of copper at a 80°C is placed in an insulated cup
containing 10g of water at a temperature 50°C. (The specific heat of copper is 0.385 J/g°C and the specific heat of
water is 4.18J/ g°C.). After heat was transferred to the water from the copper it was noticed that the temperature of
the copper changed more than the temperature of the water since it had a lower specific heat capacity
Questions/Main Ideas
Objective Calculate the heat of a reaction and explain if a reaction is exothermic or
endothermic
Calculating heat of a solution
• to calculate you need to know the specific heat capacity of the substance (c),
the mass of solution (m) (solute +solvent) and the change in temperature(∆t
which is final temperature – initial temperature)
Ex. 1 Water only
Calculate the heat absorbed by 100g of water when it has its temperature raised by a
chemical reaction from 30˚C to 50˚C. Specific heat capacity of water is 4.18J/˚C g.
q= mc∆T = 100g (4.18J/˚C g) (50˚C− 30˚C) = 8360 J
Ex. 2 Water and chemical
80g of sodium hydroxide dissolves in 120g of water and causes an increase in
temperature from 20˚C to 30˚C. Calculate the heat of the reaction.
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Key Questions
1) What is the amount of heat released when 10 grams of a ammonium chloride
causes the temperature of 40 grams of water to go from 30˚C to 10 ˚C ?
2) Why does it take longer to boil a gallon of water compared to a cup of water?
3)Which would reach 100 ˚C faster, 50g of a piece of iron or 50g of water?
A. System and surroundings
1) Exothermic
-“exit” of heat
- energy flows out of system (ex. Fire)
2) Endothermic
- “entrance” of heat
- energy flows into system (ice melting)
Chemical Reaction in water
• All data collected from experiments carried out in water is from point
of view of water
Calorimetry
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Calorimeter
Changes in energy due to state changes
CER 7 Determine if you agree or disagree with the statement below and provide at least 2 pieces of
evidence and your reasoning to support your view. I add 20g of NaOH to 80g of water and I notice that
the temperature rises from 25°C to 28°C. I calculate the heat of the reaction as 250.8J which means the
reaction is Endothermic and is absorbing energy from the surroundings
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Questions/Main Ideas
Objective Draw a heating and cooling curve to show the energy associated with a
substance going from a solid to a liquid and a gas.
What are some things that happen as we heat a sample up?
Heat


In chemistry heat is measured in Joules (J) and is transfer of energy
Heat is dependent on mass, temperature change and specific heat (or ability
of a substance to absorb heat)
Temperature is a measure of warmth or coldness.
What is the heating curve?
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Why is the curve flat at some portions?
What can you determine at flat lines?
What is heat of fusion? What is heat of vaporization?
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Summary
• The heating curve is a useful tool to show us the changes in
temperature, energy, and state as a sample is heated up.
Cooling Curve
Using the heating curve of water as a guide, draw a cooling curve for water
beginning with steam at 140°C and ending at -40°C. Indicate on your graph
at which points KE or PE changes
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