Transcript Chapter 14: Solutions

Ch. 14 SOLUTIONS
GCC
CHM 130
What is a solution?
• solution - A solute dissolved in a solvent
– solute - chemical there’s less of
– solvent - chemical there’s more of
• Water is the most common solvent.
Physical states of solute and
solvent can be solid, liquid or gas
Examples:
Gas in Liquid
Liquid in Liquid
Solid in Liquid
Gas in Gas
Solid in Solid
Carbonated Soda
Vodka and tonic
Salt Water
Air (N2 + O2 + trace gas)
Steel (Fe + C)
14.1 Gas solubility in liquids
1. Temperature: Solubility of a gas in a
decreases
liquid ___________as
T increases.
T increases, gas molecules move
faster, escape from surface easier.
Think about what happens if you open a
can of soda that has been sitting outside
for a few hours on a hot Summer day?
increases
2) Pressure: Solubility of a gas __________
as the pressure increases.
Higher pressure keeps the liquid
molecules from escaping into gas by
pushing down on them.
Another example – as divers
descend in the ocean, the
solubility of air in blood increases
Solid Solubility in liquids
• The solubility of a solid will _________
increase
as the temperature increases.
As T increases, molecules move faster
and pull apart the ions in an ionic solid,
so it dissolves faster as well.
The solubility of a solid is not
affected by pressure, unlike a gas.
14.2 Liquids in liquids
“Like dissolves like” rule
 Polar solutes dissolve in polar solvents
 Nonpolar dissolves in nonpolar
 Nonpolar and polar don’t mix
When two liquids mix we call them
miscible, if they don’t mix they are immiscible
14.3 Solids in liquids
“Like dissolves like” rule
 Polar solutes dissolve in polar solvents
 Nonpolar dissolves in nonpolar
 Nonpolar and polar don’t mix
If a solid dissolves it is soluble, if not it is
insoluble
Note - Solubility rules are for ionic solid
solutes in water solvent!!! But not all solvents
are water….
Will these solutes dissolve in
these solvents?
Solvent
Solute
HCl
Solute
I2
Solute
PCl3
Solute
CH4
NH3
Y
No
Y
No
C12H26
No
Y
No
Y
Br2
No
Y
No
Y
Miscible, immiscible, soluble or insoluble
Solutes i
polar liquid
nonpolar liquid
polar solvent
miscible
immiscible
immiscible
miscible
polar solid
soluble
nonpolar solid
insoluble
ionic solid
nonpolar solvent
Check Solubility
Rules!
insoluble
soluble
insoluble
Which is soluble in oil? I2, P4, grease
Which is miscible in oil? CCl4
(Hint – is oil polar or nonpolar?)
nonpolar
I2(s)
ionic
KCl (s)
nonpolar
P4 (s)
grease(s) nonpolar
polar
HBr (l)
CCl4 (l) nonpolar
Nonpolar
chemicals mix
with oil – “like
dissolves like”
14.4 THE DISSOLVING PROCESS
• solvent molecules pull the solute
molecules from each other if the solutesolvent attraction is greater than the
solute-solute attraction
•
http://www.northland.cc.mn.us/biology/Biology1111/animations/dissolve.html
•
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf
•
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/thermochem/solutionSalt.html
14.8 Concentration
• concentrated solution – lots of solute
• dilute solution – little solute
• If your drink is “strong,” it is
concentrated. If your coffee is
“weak,” it is dilute.
Concentration
• The amount of solute in solvent is
the concentration.
• Units for concentration:
- Mass Percent (%)
- Molarity (M)
14.8 Mass %
 x 100
gramssolute
= 
 gramssolute  gramssolvent


Ex: Calc. the mass % for 15.0 grams of
potassium nitrate being dissolved in
135 grams of water.
Mass % = (15.0g / 15.0+135g) x 100
= 10.0%
Ex: How many grams of water are needed
to make a 5.00% saline solution with
10.0 grams of salt?
First set up: 5.00% =  10.0  (100)
 10.0 x 
5.00 (10.0 + x) = 10.0 (100)
5.00 (10.0 + x) = 1000
10.0 + x = 1000 / 5.00
10.0 + x = 200
X = 1.90x102 grams
check: 5.00 = (10/200) (100)
Yes
14.9 Molarity
• MOLARITY (M) = moles per liter
M =
moles solute = mol
liters of solution
L
Ex: Calculate the molarity if 9.99 grams
of potassium bromide is dissolved in
2.50 liters of water.
9.99 g KBr ( mol / 119.00 g) = 0.08395 mol
M = 0.08395 mol / 2.50 L = 0.0336 mol/L
Do the questions in the online notes and
worksheet !!!
Self Test
• Page 410
• Try 1-4, 8-9, 13-15
• Answers in Appendix J