solutions
DESCRIPTION
Solutions . Solutions . A solution is a homogeneous mixture of 2 or more substances in a single phase. One constituent is usually regarded as the SOLVENT and the others as SOLUTES . Solution. Solvent. Solute. Parts of a Solution. - PowerPoint PPT PresentationTRANSCRIPT
PowerPoint Presentation
Solutions
Solutions
A solution is a homogeneous mixture of 2 or more substances in a single phase.
One constituent is usually regarded as the SOLVENT and the others as SOLUTES.
Parts of a Solution
SOLUTE the part of a solution that is being dissolved (usually the lesser amount)
SOLVENT the part of a solution that dissolves the solute (usually the greater amount)
Solute + Solvent = Solution
Solvent
Solute
Solution
4
Nature of Solutes in Solutions
Spread evenly throughout the solution
Cannot be separated by filtration
Can be separated by evaporation
Not visible, solution appears transparent
May give a color to the solution
Gas in a Gas Air
Gas in a Liquid Soda
Liquid in a LiquidGasoline
Solid in a Liquid Sea Water
Solids in Solids Brass
salad
soil
water
Solutions
Examples
Non-Examples
Water is the universal solvent
because more substances dissolve in water than in any other chemical.
This has to do with the polarity of each water molecule.
Molecular Polarity
Nonpolar molecules:
-- e are shared equally
e.g.,
e.g.,
Polar molecules:
-- e NOT shared equally
fats and oils
HCH
H
HCH
HCH
HCH
H
water
H
H
O
Water Molecules
Are polar because O is more electronegative than H
Gives O a partial negative charge.
Form strong intermolecular hydrogen bonds.
Water molecules are attracted to one another better than other molecules its size.
8
9
Hydrogen bonding
animation
Hydrogen bonding occurs because of polarity
One water molecule bonds to another.
Surface Tension
Because of the hydrogen bonds, water molecules are attracted to each other.
Liquid water acts like it has a skin.
Water forms round drops.
10
Properties of Water
Hydrogen bonding causes:
High surface tension
Low vapor pressure
High specific heat capacity
High heat of vaporization
High boiling point
Strongest intermolecular force was hydrogen bond- review other forces
Heat capacity reflects on how fast molecules move.
Heat of vaporization- in order to evaporate you have to break the hydrogen bond- huge amount to break the bonds for vaporization temperature
11
Properties of Water
When it freezs the hydrogen bond becomes stronger- forms a hexagonal structure which takes more space
12
What is, or is not, soluble in H20?
Polar solvents dissolve ionic compounds and polar molecules
Water is polar therefore it can dissolve
NaCl
Copper (II) sulfate
NaOH
Nonpolar solvents dissolve nonpolar compounds
Oil is nonpolar, which is why oil and water separate
Like Dissolves Like
Animations of the Solvation(Animation of a Solute Dissolving)
While you watch each video clip, record your observations on your notes.
Animation of Salt Dissolving in Water
Animation of Sugar Dissolving in Water
Username: htaccess
Password: tiger.core
15
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
Animation
When Ionic Solids Dissolve
16
How do we know ions are present in aqueous solutions?
The solutions can conduct electricity
They are called ELECTROLYTES
HCl, MgCl2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions.
Aqueous Solutions
18
Electrolyte vs. Non-Electrolyte
Salt
(Ionic Solids)
Sugar
(Molecular Solids)
Both
Water is
the solvent.
Broke apart into ions
Broke apart into whole molecules
Was able to light the light bulb
an electrolyte
An electrolyte is a substance when dissolved in water can conduct an electric current.
Forms a
solution
Did not light the light bulb
a non-electrolyte
Cant Conduct an Electric Current
Can Conduct an Electric Current
A non-electrolyte is a substance when dissolved in water cant conduct an electric current.
Rate of Solution = How Fast
Exploration
To an empty 250mL beaker, add approximately 100mL of warm-hot water from a hot plate.
To an empty 250mL beaker, add approximately 100mL of ice water. Be sure to leave the ice behind!
Add a sugar cube to each of the 250mL beakers. Observe what happens.
Record your observations on your notes.
List other ways that you believe that you could make a solute dissolve more quickly.
Electrolytes in the Body
Carry messages to and from the brain as electrical signals
Maintain cellular function with the correct concentrations electrolytes
Make your own50-70 g sugarOne liter of warm waterPinch of salt200ml of sugar free fruit squashMix, cool and drinkRate of Solution
What are ways that you make a solute dissolve faster?
Increase the temperature.
Crush or use smaller size solute particles.
Stir the solutions.
Solubility = How Much
Type of SoluteTemperaturePressureSolid SoluteGaseous SoluteSolubility generally increases as temperature increases.
Pressure has no effect on the solubility of a solid.
Solubility generally decreases as temperature increases.
Solubility generally increases as pressure increases.
For gases, it may be helpful to have students think of soda. You keep soda in the refrigerator (low temps) and closed (keep pressure up).
23
Types of Solutions
There are three ways to classify a solution.
Unsaturated Solutions
Saturated Solutions
Supersaturated Solutions
Types of Solutions
Type of SolutionDescriptionPictureRelation to Solubility CurveUnsaturatedSaturatedSupersaturatedA solution in which more solute can dissolve
Below the
Line
A solution in which contains the maximum amount of solute
On the
Line
A solution in which contains more than the maximum amount of solute
Above the
Line
See PDF for pictures
25
Supersaturated
The solution is holding more solute than it should be able to. This is achieved by heating the solution and then cooling it slowly.
Examples: rock candy, southern style sweet tea, chemical heat packs
Supersaturated solutions are unstable. The supersaturation is only temporary
Solubility
SATURATED SOLUTION
no more solute dissolves
UNSATURATED SOLUTION
more solute dissolves
SUPERSATURATED SOLUTION
becomes unstable, crystals form
increasing concentration
27
Supersaturated
Solubility Curves
Solubility indicates the amount of solute that will dissolve in a given amount of solvent at a specific temperature.
For this curve,
X-Axis
Temperature
Y-Axis
How Much Solute Dissolves in 100g of Water
Various Lines
Each line represents a different solute.
Solubility Curves
CO2
Saturated
Supersaturated
Unsaturated
Using an available solubility
curve, classify as
unsaturated, saturated,
or supersaturated.
80 g NaNO3 @ 30oC
45 g KCl @ 60oC
30 g KClO3 @ 30oC
70 g Pb(NO3)2 @ 60oC
per 100 g H2O
unsaturated
saturated
supersaturated
unsaturated
Describe each situation below.
(A) Per 100 g H2O,
100 g NaNO3 @ 50oC.
(B) Cool solution (A) very
slowly to 10oC.
(C) Quench solution (A) in
an ice bath to 10oC.
unsaturated;
all solute dissolves;
clear solution.
supersaturated;
extra solute remains
in solution; still clear
saturated; extra solute (20 g)
cant remain in solution and becomes visible
How to use a solubility graph?
A.IDENTIFYING A SUBSTANCE ( given the solubility in g/100 cm3 of water and the temperature)
Look for the intersection of the solubility and temperature.
33
Using Solubility Curves
How much KNO3 would dissolve in 100g of water at 50oC?
How much NH4Cl would dissolve in 200g of water at 70oC?
At what temperature would 22g of KCl be able to dissolve in 50g of water?
Which is more soluble (has a higher solubility) at 40oC?
NH3
KClO3
84g
120g
68oC
Learning Check :What substance has a solubility of 90 g/100 cm3 in water at a temperature of 25C ?
35
36
Learning Check :
What substance has a solubility of 200 g/100 cm3 of water at a temperature of 90C ?
37
38
Look for the temperature or solubility
Locate the solubility curve needed and see for a given temperature, which solubility it lines up with and visa versa.
39
Learning Check:
What is the solubility of potassium nitrate at 80C ?
40
What is the solubility of potassium nitrate at 80C ?
41
Learning Check :
At what temperature will sodium nitrate have a solubility of 95 g/100 cm3 ?
42
Learning Check:
At what temperature will sodium nitrate have a solubility of 95 g/100 cm3 ?
43
Learning Check:
At what temperature will potassium iodide have a solubility of 230 g/100 cm3 ?
44
Learning Check:
At what temperature will potassium iodide have a solubility of 130 g/100 cm3 ?
45
Using Solubility Curves:
What is the solubility of sodium chloride at 25C in 100 cm3 of water ?
From the solubility graph we see that sodium chlorides solubility is 36 g.
46
SOLUBLE OR INSOLUBLE?
Soluble:
able to be dissolved
Insoluble:
does not dissolve in solution (or water)
Precipitate:
an insoluble solid formed when two solutions are mixed
Double Replacement reactions
AB + CD AD + CB
NaCl + AgNO3 NaNO3 + AgCl
Concentration of Solute
The amount of solute in a solution is given by its concentration.
Molarity
(
M
)
=
moles solute
liters of solution
PROBLEM: Dissolve 5.00 g of NiCl26 H2O in enough water to make 250 mL of solution. Calculate the Molarity.
Step 1: Calculate moles of NiCl26H2O
Step 2: Calculate Molarity
[NiCl26 H2O ] = 0.0841 M
Known
Mass=5 g
Volume = 0.250 L
Unknown
Molarity of
NiCl26 H2O ?
Analysis
molar mass = 237.7 g
M= n/ V;
0.0125 mol H2C2O4 x (90.00 g/mol) = 1.13 g H2C2O4
1 mol H2C2O4
MOLARITY PROBLEM
What mass of oxalic acid, H2C2O4, is required to make 250. mL of a 0.0500 M solution?
Known
Volume = 0.250 L
M = 0.0500 moles/L
Unknown
g of H2C2O4,?
Analysis
molar mass = 90.00 g
M= mol/ V;
Step 1: Calculate moles of H2C2O4
(0.0500 mol/L) x (0.250 L) = 0.0125 moles
Step 2: Convert moles to grams
Learning Check
How many grams of NaOH are required to prepare 400. mL of 3.0 M NaOH solution?
1)12 g
2)48 g
3) 300 g
Making Molar Solutions
from liquids
(More accurately, from stock solutions)
54
Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution.
Dilution
Add Solvent
Moles of solute
before dilution (i)
Moles of solute
after dilution (f)
=
MiVi
MfVf
=
4.5
Making a Dilute Solution
Timberlake, Chemistry 7th Edition, page 344
initial solution
remove
sample
diluted solution
same number of
moles of solute
in a larger volume
mix
moles of
solute
56
Dilution
Preparation of a desired solution by adding water to a concentrate.
Moles of solute remain the same.
57
Dilution Practice Problem
What volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution?
Known
Molarity1 = 15.8 mol/L of HNO3
Volume2 = 250 mL
Molarity2 = 6.0 mol/L of HNO3
Unknown
Volume of HNO3?
Equation
M1V1 = M2V2
Solution :
V1 = (6.0 mol/L x 0.250 L) / 15.8 M = 0.095 L
58
If we have 1 L of 3 M HCl, what is M if we dilute acid to 6 L?
Known
Molarity1 = 3 mol/L
Volume1 = 1 L of HCl
Volume2 = 6L of HCl
Unknown
Molarity of HCl?
Equation
M1V1 = M2V2;
Solution :
M2 = (3 mol/L x 1 L) / (6 L) = 0.5 M
Dilution Practice Problem
What volume of 0.5 M HCl can be prepared from 1 L of
12 M HCl?
Solution :
V2 = (12 mol/L x 1 L) / (0.5 L) = 24 L
Known
Volume1 = 1 L of HCl
Molarity1 = 12 mol/L of HCl
Molarity2 = 0.5 mol/L of HCl
Unknown
Volume of HCl?
Equation
M1V1 = M2V2
Dilution Practice Problem
61
5
.00 g
1 mol
237.7 g
=
0.0210 mol
0.0210 mol
0.250 L
=
0.0841 M
2
2
1
1
V
M
V
M
=