4.
Solvation – the process of dissolving
solute particles are surrounded by
solvent particles
solute particles are separated and
pulled into solution
11.
Solubility
› maximum grams of solute that will dissolve in
100 g of solvent at a given temperature
› varies with temp
› based on a saturated solution
13.
Solids are more soluble at...
› high temperatures.
Gases are more soluble at...
low
temperatures &
high pressures (Henry’s
Law).
EX: nitrogen narcosis, the
“bends,” soda
14.
15.
The amount of solute in a solution.
How can we describe or communicate
concentration?
› Qualitatively through words
(“black” coffee vs. “a light amber shade”)
› Quantitatively through numbers
(2 sugars & 1 cream)
16. With Percent (%)
% by mass
› Medicated creams
› Proactiv contains 2.5%
benzoyl peroxide by
mass
% by volume
With Moles*
Molarity (M)
Molality (m)
Mole Fraction (X)
** Most often used by chemists **
› Usually used when both
solute & solvent are
liquids
› Gasoline can contain
up to 10% ethanol by
volume
Parts
› ppm, ppb - water
contaminants
(don’t talk about in here)
17. moles of solute
molarity (M)
L of solution
% m/v
mass of solute (grams)
volume of solution (mL)
% v/v
volum e of solute
total volum e of solution
% m/m
mass of solute (grams)
mass of solution (grams)
Remember to multiply the % formulas by 100 OR move decimal two spots left
Moles of solute
Mole Fraction
Moles of solution
18. moles of solute
molality (m)
kg of solvent
0.25 mol
0.25m
1 kg
mass of solvent only
1 kg water = 1 L water
M 1V1 M 2V2
19.
Find the molality of a solution containing 75
g of MgCl2 in 250 mL of water.
75 g MgCl2
1 mol MgCl2
95.21 g MgCl2 0.25 kg water
mol
m
kg
= 3.2m MgCl2
20.
How many grams of NaCl are req’d to make
a 1.54m solution using 0.500 kg of water?
0.500 kg water
1.54 mol NaCl
58.44 g NaCl
1 kg water
1 mol NaCl
1.5 mol
1.5m
1 kg
= 45.0 g NaCl
21.
At a restaurant I saw a man put 7 packets
of sugar into his cup of coffee. What is the
percent by mass of sugar in this poor man’s
coffee?
› 1 packet of sugar = 4 grams
› 1 cup of coffee = 180 grams
28 g sugar
(180 + 28) g
= 13.5% sugar
22.
Find the mole fraction of sugar in the coffee
of that now comatose man who has just
come down off his 7 sugar packet high.
› 0.08 moles sugar
› 10 moles coffee
Xsugar =
0.08 moles sugar
(10 + 0.08) total moles
= 0.0079
Xcoffee = 1 – Xsugar = 1 – 0.0079 = 0.9921
23. What is the mole fraction of each component in a solution
in which 3.57 g of sodium chloride, NaCl, is dissolved in
25.0 g of water?
First, convert from mass of NaCl to moles of NaCl.
3.57 g NaCl x 1 mole NaCl
=
0.0610857139 mole NaCl
58.44247 g NaCl
Next, convert from mass of water to moles of water.
25.0 g H2O x 1 mole H2O
=
1.387710877 mole H2O
18.01528 g H2O
Substitute these two quantities into the defining equation for mole fraction.
XNaCl =
0.0610857139 mole NaCl
= 0.0421630713 ~ 0.042
(0.0610857139 + 1.387710877) mol solution
Xwater =
1.387710877 mole H20
= 0.9578369287 ~ 0.96
(0.0610857139 + 1.387710877) mol solution
** Note the sum of the mole fractions for a solution will equal 1. **
24. Preparation of a desired solution by
adding water to a concentrate.
Moles of solute remain the same.
M 1V1 M 2V2
25.
What volume of 15.8M HNO3 is required
to make 250 mL of a 6.0M solution?
GIVEN:
M1 = 15.8M
V1 = ?
M2 = 6.0M
V2 = 250 mL
WORK:
M1 V1 = M2 V2
(15.8M) V1 = (6.0M)(250mL)
V1 = 95 mL of 15.8M HNO3
26.
1.54m NaCl in
0.500 kg of water
mass 45.0 g of NaCl
add 0.500 kg of water
500 mL of 1.54M NaCl
mass 45.0 g of NaCl
add water until total
volume is 500 mL
500 mL
water
45.0 g
NaCl
500 mL
mark
500 mL
volumetric
flask
27.
250 mL of 6.0M HNO3
by dilution
95 mL of
15.8M HNO3
› measure 95 mL
of 15.8M HNO3
combine with water until total
volume is 250 mL
Safety: “Do as you oughtta,
add the acid to the watta!”
250 mL
mark
water
for
safety
28.
Turn in one paper per team.
Complete the following steps:
A) Show the necessary calculations.
B) Write out directions for preparing the solution.
C) Prepare the solution.
For each of the following solutions:
1) 100.0 mL of 0.50M NaCl
2) 0.25m NaCl in 100.0 mL of water
3) 100.0 mL of 3.0M HCl from 12.1M concentrate.
31.
Freezing Point Depression (tf)
› f.p. of a solution is lower than f.p. of the pure
solvent
Boiling Point Elevation (tb)
› b.p. of a solution is higher than b.p. of the
pure solvent
35. t = k · m · n
t: change in temperature ( C)
k: constant based on the solvent ( C·kg/mol)
m: molality (m)
n: # of particles
36.
# of Particles
› Nonelectrolytes (covalent)
remain intact when dissolved
1 particle
› Electrolytes (ionic)
dissociate into ions when dissolved
2 or more particles
37.
At what temperature will a solution that is
composed of 0.73 moles of glucose in 225 g
of phenol boil?
GIVEN:
WORK:
b.p. = ?
m = 0.73mol ÷ 0.225kg
tb = ?
tb = (3.60°C·kg/mol)(3.2m)(1)
kb = 3.60°C·kg/mol
tb = 12°C
m = 3.2m
b.p. = 181.8°C + 12°C
n=1
b.p. = 194°C
tb = kb · m · n
38.
Find the freezing point of a saturated solution
of NaCl containing 28 g NaCl in 100. mL water.
GIVEN:
f.p. = ?
tf = ?
kf = 1.86°C·kg/mol
WORK:
m = 0.48mol ÷ 0.100kg
tf = (1.86°C·kg/mol)(4.8m)(2)
m = 4.8m
n=2
tf = kf · m · n
f.p. = 0.00°C - 18°C
tf = 18°C
f.p. = -18°C
39.
40.
Once you write the molecular equation (synthesis,
decomposition, etc.), you should check for
reactants and products that are soluble or
insoluble (determine states of matter, which stay
the same throughout reaction).
Use a solubility table to tell us what compounds are
aqueous (dissolved in water), solids, liquids, and/or
gases
We usually assume the reaction is in water
If the compound is soluble (does dissolve in water),
the the compound splits into its ions
If the compound is insoluble (does NOT dissolve in
water), then it remains as a compound
41. 1.
2.
3.
Write a balanced chemical (molecular) equation
Consult the solubility rules (along with strong acids and
strong bases) and assign the correct state of matter
symbol annotation
Write the Total Ionic Equation (T.I.E)
a.
4.
Eliminate spectator ions
a.
b.
5.
All compounds that are annotated (aq) break up into
individual cations and anions in that order
Spectator ions-those ions that do not participate in the
chemical reaction but are present in the reaction mixture
Spectator ions are in the same form on each side of the
equation arrow
Write the Net Ionic Equation (N.I.E)
a.
The convention is to write the cation first followed by the anion
on the reactants side
45. Potassium chromate mixes with lead (II) nitrate
Molecular Equation:
K2CrO4 + Pb(NO3)2
Soluble
Soluble
PbCrO4 + 2 KNO3
Insoluble
Total Ionic Equation:
2 K+ + CrO4 -2 + Pb+2 + 2 NO3-
PbCrO4 (s) + 2 K+ + 2 NO3Net Ionic Equation:
CrO4 -2 + Pb+2 PbCrO4 (s)
Soluble
46. Balanced Chemical Equation:
Pb(NO3)2(aq) + 2NaI(aq) PbI2(s) + 2NaNO3(aq)
“Complete Ionic” Equation:
Pb2+(aq) + 2NO3-(aq) + 2Na+(aq)+ 2I-(aq) PbI2(s) + 2Na+(aq) + 2NO3(aq)
Cancel the “spectator ions” that appear on both sides of the
arrow
Pb2+(aq) + 2NO3-(aq) + 2Na+(aq)+ 2I-(aq) PbI2(s) + 2Na+(aq) + 2NO3(aq)
“Net Ionic” Equation:
Pb2+(aq) + 2I-(aq) PbI2(s)
47. States of matter assigned in the
molecular equation stay the same
throughout the T.I.E. and the N.I.E.
Solids, liquids, and gases DO NOT ionize
Gases keep their subscript (it doesn’t
become a coefficient like other
compounds)
› For example: H2, Br2, Cl2, etc. stay like this
They don’t become 2H-1, 2Br -1, 2Cl -1