SOLUTIONS
Honors
Chemistry
Snarrenberg
2012-2013
CATALYST: TUESDAY 5/28
Think back to when you did the polarity demo in lab with
Styrofoam and eco-peanuts…
Think back to Chapter 3…








What is a solution?
What do you call the substance you’re dissolving?
What do you call the substance you’re dissolving it in ?
How do you tell which is which ?
What is an aqueous solution ?
How do ionic compounds dissolve in water?
How do covalent compounds dissolve in water?
Can you think of a substance that doesn’t dissolve in water?
What causes them to not dissolve?
SOAP
 After you eat fried chicken for dinner, (or pizza or steak or…
anyone hungry yet?), and you’re asked to do the dishes, why
do you have to use soap?
 Why can’t you just use water?
 But then how does the soap come of f?
LET’S LOOK AT THE VOCAB 
 Define the following using the words ‘solute’ and ‘solvent’
 Saturated solution
 Unsaturated solution
 Concentrated solution
 Dilute solution
 Demo time dudes!
-
An aqueous solution
containing 30 g of KCl in 50 g
of water at 55°C is…
1) Unsaturated
2) Saturated
3) Supersaturated
-
An aqueous solution
containing 5 g of NaNO3 in 10
g of water at STP is…
1) Unsaturated
2) Saturated
3) Supersaturated
-
An aqueous solution
containing 25 g of NaNO3 in
50 g of water at72°C is…
1) Unsaturated
2) Saturated
3) Supersaturated
DEMO QUESTIONS
 Is the solution saturated or unsaturated?
 Is the solution concentrated or dilute?
 What happens as the solution is heated?
 ..but wait, wasn’t it saturated already?
 What happens as the solution cools?
 What happens when a crystal of solid is added?
COMPARING FLASKS
 Draw a qualitative picture to represent the concentration in
each flask.
 How could you quantify the concentration in the flasks?
-
Which salt has the highest solubility at STP?
Which salt has the lowest solubility at STP?
If you have 50 g of water, how many grams of lead (II) nitrate will make a
saturated solution?
Catalyst:
Thu 5/30
HW Tonight:
38, 40, 50
-
How many grams of sodium acetate can dissolve in 100 g of water at 25°C?
How many grams of sodium acetate can dissolve in 50 g of water at 25°C?
At around what temperature can I dissolve 140 g of sodium acetate to make a
saturated solution?
QUANTIFYING IT!
 How do you quantify the concentration of a solution?
 Molarity! (M) – mol/L
 1 .0 molar solution, written as 1 .0 M, contains 1 .0 mols of
solute per liter of solution
CALCULATING MOLARIT Y
 What is the molarity of a solution containing 11 .5 g of NaOH
with a volume of 1 .50 L?
 M = moles of solute
liters of solution
11.5 g NaOH
1 mol NaOH
= 0.288 mol NaOH
40.0 g NaOH
 M = 0.288 mol NaOH = 0.192 M NaOH
1 .50 L solution
PREPARATION OF A STANDARD
SOLUTION
Standard solution: a solution whose concentration is accurately known
CALCULATING MOLARIT Y
 Calculate the molarity
of a solution prepared
by dissolving 15.6 g
of solid KBr in enough
water to make 1.25 L
of solution
 0.105 M
 Calculate the molarity
of a solution prepared
by dissolving 250.0 g
of solid Ca(NO 3 ) 2 in
enough water to make
2500 mL of solution
 0.00061 M
 0.61 M
POGIL QUESTION
A student correctly determines that 17.1 grams of
sucrose are needed to make 50 mL of a 1 M sucrose solution.
When making this solution in lab, the student measured 50 mL
of water and massed 17.1 grams of sucrose. The student then
mixed the two together into a new beaker. The student’s
resulting solution was not 1 M sucrose as intended. After the
student mixed sucrose and water, the resulting solution was
poured into a graduated cylinder and it read 62 mL.
a) What part of the molarity equation did the student overlook
when mixing the solution ?
a) What steps should the student take in lab to correctly
prepare the 1 M solution?
NOTE ON MOLARIT Y
 How many mols of NaCl are in a 1 .0 M NaCl solution?
 …actually, there are no NaCl units in a NaCl solution, only Na+
ions and Cl- ions
 1 .0 mols Na+ === 1 .0 M Na+
 1 .0 mols Cl- === 1 .0 M Cl Net ionic equations
CONCENTRATION OF IONS IN SOLUTION
1.20 M Na 2 SO 4
2.40 M Na +
1.20 M SO 4 2-
0.750 M K 2 CrO 4
1.50 M K +
0.750 M CrO 4 2-
CALCULATING # MOLS FROM MOLARIT Y
 Molarity has a complex unit ( mol/L) and can be used as a
conversion factor! (You must be so excited XD)
 How many mols of Ag + ions are in 25 mL of a 0.75 M AgNO 3
solution?
 0.75 M AgNO 3 = 0.75 M Ag +
25 mL
1L
0.75 mol Ag+
1000 mL
1 L solution (exactly)
= 1.9 x 10-2 mol Ag+
YOU TRY 
 How many moles of
Na + ions are present
in 42.0 mL of a 0.350
M NaCl solution?
 How many mols of
Na + ions are present
in 42.0 mL of a 0.350
M Na3PO4 solution?
 1.47 x 10 -2 mol Na +
 4.41 x 10 -2 mol Na +
CALCULATING MASS FROM MOLARIT Y
 What mass of NaNO 3
is required to make
2.50 L of 0.150 M
solution of NaNO 3 ?
 What mass of
(NH 4 ) 2 SO 4 is required
to make 1.25 L of a
0.250 M solution of
(NH 4 ) 2 SO 4 ?
 31.9 g
 41.3 g
HW Check
• #54: the new concentration of solute is half the original
• #58: 0.541 L
• #60: 0.13 M
• #62: 10.3 mL
• Dilutions Review: key words to watch out for that indicate
a dilutions problem with M1V1=M2V2
• A change in molarity of the solutions with the same solute
• Concentrated / Dilute
• New solution / original solution
HW Review
Catalyst: Monday 6/2
• Draw a stoichiometry map (remember, the center link is
always Mol A <--> Mol B) to include molarity. Think about
all the units you can come from and go to.
• HW: 66, 67, 68 (Ch. 15)
• Quiz Thursday on Solubility (graph), Molarity, Dilutions,
and Solutions Stoich
Stoichiometry Review
Propane, used in gas barbecue grills, burns in oxygen
according to the following balanced chemical equation:
C3H8(g) + 5O2(g)  3CO2 (g) 4H2O
Calculate the mass in grams of water vapor produced if
3.11 mol of propane is burned.
ANSWER: 224 g
Catalyst: Monday 6/2
• Draw a stoichiometry map (remember, the center link is
always Mol A <--> Mol B) to include molarity. Think about
all the units you can come from and go to.
• What if you started with L of a solution or you needed to
go to L or of a solution? Now add a new bridge.
• If we are dealing with reactions where the reactants are
aqueous solutions, what TYPE of reaction are we talking
about? (oooh throw back)
Solutions Stoichiometry #1
silver nitrate + potassium chloride  ?
Solutions Stoichiometry #1
• If I mixed 2 mL of 1.5 M silver nitrate with excess
potassium chloride, how many grams of solid silver
chloride was I able to produce?
Answer: 0.43 g
Solutions Stoichiometry #3
Limiting Reactant Problem!
Calculate the mass of the white solid CaCO3 that forms
when 25.0 mL of a 0.100 M Ca(NO3)2 solution is mixed with
20.0 mL of a 0.150 M Na2CO3 solution.
Answer: 0.250 g CaCO3
Announcements
• Quiz Thursday on Solubility (graph), Molarity, Dilutions,
and Solutions Stoich
• HW: 15.7 Notes & #65
Solutions Stoich #4
aluminum + copper (II) chloride  ?
HW Answers:
• #66 – 0.523 g
• #67 – 0.976 g PbCrO4
• #68 – 0.300 g
Brainstorm
• What pieces of information do you need to find the
molarity of the copper (II) chloride solution?
• What tools in your toolbox can you use to get those
pieces of information? (Hint: one you can find directly, the
other must be found indirectly, i.e. through calculation)
Some info…
• Volume of CuCl2 solution used: 20.0 mL
• Mass of Al before the reaction: 0.59 g
• Aluminum is the excess reactant!
% Error Calculation
• The actual molarity of the CuCl2 solution was 0.65. What
was the percent error?
Try this one… Solutions Stoich #5
One way to determine the amount of chloride ion in
a a water sample is to titrate the sample of standard AgNO3
solution to produce solid AgCl.
Ag+(aq) + Cl-(aq)  AgCl(s)
If a 25.0 mL water sample requires 27.2 mL of 0.104
M AgNO3 in such a titration, what is the concentration of Clin the sample?
Answer: 0.113 M
Solutions Stoichiometry #2
• Calculate the mass of sodium iodide that must be added
to 425.0 mL of a 0.100 M lead (II) nitrate solution to
precipitate all of the lead (II) ions as lead (II) iodide.
Answer: 12.7 g NaI