solution: a homogeneous mixture solute: substance that gets dissolved solvent: substance that does...
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Transcript of solution: a homogeneous mixture solute: substance that gets dissolved solvent: substance that does...
solution:
a homogeneous mixture
solute: substance that gets dissolved
solvent: substance that does the dissolving
tincture: sol’n in which alcohol is solvent
aqueous: water is solvent
water is an excellent solvent because of its polarity
salt dissolving in water
hydrochloric acid dissolving in water
δ+ HCl δ-δ+ HCl δ-
“like dissolves like”
polar mixes w/ polar; nonpolar w/nonpolar
miscible: two liquids that mixex: water and alcohol
immiscible: liquids that don’t mix
ex: water and oil
types of compounds that dissolve in water
I. Ionic (metal w/nonmetal) ex: NaCl, KI
II. Acids (H+ w/ anion) ex: HCl, H2SO4
III. polar covalent ex: NH3, H2O2
cmpds w/ -OH groups ex: sugars, alcohols
ethanol: glucose: C6H12O6C2H5OH
compounds that don’t dissolve in water
nonpolar covalent cmpds
ex: hydrocarbons like C4H10
symmetrical molecules like CCl4
Conductivity of Solutions
Electrolyte:
cmpd that dissociates into ions; conducts electricity
must be ionic cmpd or an acid ex: CuSO4, HNO3
nonelectrolyte: doesn’t dissociate; won’tconduct
covalent cmpds that are not acids
ex: sugar, C12H22O11
alcohols, C2H5OH
Sample problems: determine formula,classify as soluble or insoluble, electrolyte or non
acetic acid HC2H3O2 sol. elec.
calcium chloride CaCl2 sol. elec.
Hexane, C6H14 insol. nonelec
silver nitrate
methanol
hydrochloric acid
butane
potassium iodide
AgNO3 sol, elec
CH3OH sol, nonelec
HCl sol, elec
KI sol, elec
C4H10 insol, nonelec
saturated, unsaturated, supersaturated
saturated sol’n:
contains the maximum amt of dissolved solute;equilibrium btwn dissolved and undissolved solute
unsaturated sol’n:contains less than max. amt of solute
supersaturated sol’n
contains more than the normal amt of solute
crystallizes completely by adding a “seed”crystal of the solute.
solubility: concentration of a saturatedsol’n
ex: solubility of NaCl at 25°C is 36g/100 mL
Effect of temperature on solubilitysolid solutes:solubility increases as temp increases
Gases and solubility
Effect of temp decreasing temp (water)increases solubility of gas
Effect of pressure Increasing pressure(over the water) increasessolubility
cold, high pressure
solubility curves
What is the solubilityof ammonium chlorideat 70°C ?
61 g/100 mLHow many gramsof potassium nitratewill dissolve in 100 mL water at 50°C?
83 g
How many gramsKNO3 will saturate250 mL water at 50°?
207.5 g
100 mL of saturated potassiumchlorate sol’n is cooled from80°C to 30°C? How many gramsof solute will crystallize?
at 80°: 42 g
at 30°: 12 g
30 gHow many grams staydissolved? 12 g
a sol’n contains 20 g sodium chloride dissolved in 100 mLwater at 25°C; is it saturated,unsaturated, or supersaturated?
unsaturated
Solution Concentration
dilute: contains little solute
concentrated: contains a lot of solute
ways to indicate concentration
percent: mass of solutetotal mass sol’n
100
ppm: parts per million ppb parts per billion
Molarity (M):moles solute
Liter of sol’n
Calculating Molarity M= MOL L
What is the molarity of a sol’n made by dissolving0.25 mole of sucrose in enough water to make 100.0 mL of sol’n ?
M= 0.25 mol 0.1 L
2.5 M
What is the molarity of a sol’n that contains 30.0 grams of sodium hydroxide dissolved in 0.50 liter of sol’n?
30.0 g
g
mol1
40
0.75 mol
0.50 L1.5 M
How many moles of HCl are contained in 5.0 litersof a 6.0 M HCl solution?
M= MOL L
6.0 M X mol
5.0 LX = 30 mol
How many grams of potassium sulfate are neededto dissolve in water to make 250 mL of a 2.0-molarsolution? K2SO4
2.0 MX mol
0.25 LX = 0.5 mol
0.5 mol
1 mol
174.3 g87 g
Calculate the molarity of a solution that has 12.5 g ofglucose, C6H12O6, dissolved in 500 mL of solution.
12.5 g
g
mol1
1800.06944 mol
0.5 L0.14 M
How many moles and grams of potassium iodide would be needed to prepare 0.75 liter of a 0.15 Msolution?
0.15 M = x mol 0.75 L
X = 0.1125 mol
0.1125 mol
mol1
g16718.8 g
Diluting a Solution M1V1 M2V2
concentrated diluted
If 100.0 mL of 6.0 M NaOH solution is diluted withwater to 800.0 mL, what is the molarity of the diluted solution?
(6.0 M) (100.0 mL) (800.0 mL)M2
800 mL800 mL
M2 = 0.75 M
(12.0 M) V1 (1.0 L)(3.0 M)
12.0 M12.0 M
What volume of 12.0 M HCl solution is needed to make 1.0 liter of 3.0 M solution of HCl ?
25.0 mL of concentrated acetic acid (17 molar) arepipetted into a flask. Water is added to the 1.0 literMark. Calculate the molarity of the final solution.
V1 = 0.25 L
(17 M) (25.0 mL) (1000 mL)M2
1000 mL1000 mL
M2 = 0.43 M
Colligative PropertiesProperties that depend on the concentrationof a solution
1. Lowering of vapor pressure
a solution has a lower V.P. than the puresolvent
pure water
water +a solute
the more concentrated the greaterthe effect
2. Boiling Point Elevation
solutions have a higherB.P. than the pure solvent
more conc., higher the B.P.
100°C
B> 100°C
3. Freezing Point Depression
solutions have a lowerF.P. than the pure solvent
0°C
< 0°C
Electrolytes vs. Nonelectrolytes
electrolytes dissociate into ions;
produces a higher concentration of dissolved solute particles
NaCl Na+ + Cl-
1 mol 2 moles ions
Nonelectrolytes don’t dissociate
C12H22O11 (s) C12H22O11 (aq)
1 mol 1 mol
Electrolytes have the greater
effect onC.P. ‘s
examples:Which of these 1-molar solutions has thelowest freezing point?
AlCl3
KI
C12H22O11
Na2CO3
Al3+ + Cl-3
K+ + I-
C12H22O11
Na+ + CO3
2-2
4 ions
2 ions
1 molecule
3 ions
Which of these 1-molal solutions has thehighest boiling point?
CuSO4 LiBr Mg(NO3)2 C6H12O6
2 2 3 1
Calculating Freezing & Boiling Point
ΔT = kf m ichange in F.P.
molality
freezing pt.constant
m = mol/kg solv.
ionization factor
ΔT = kb m i
kf = 1.86°C/mkb = 0.512°C/m
Calculate the freezing & boiling point ofa 1.5-molal solution of sodium hydroxide.
F.P.
ΔT = kf m i
ΔT = (1.86 °C/m) (1.5 m) (2)
NaOH Na+ + OH-
ΔT = 5.58 °CF.P. = -5.6 °C
B.P.
ΔT = (0.512 °C/m) (1.5 m) (2)ΔT = 1.536 °C
B.P. = 101.5 °C
Calculate the freezing and boiling point of a 2.0 maqueous solution of aluminum chloride.
AlCl3 Al+ + 3 Cl- ΔT = kf m i
ΔT = kbm i
ΔT = (1.86 °C/m) (2.0 m) (4)
ΔT = (0.512 °C/m) (2.0 m) (4)
ΔT = 14.88 °CF.P. = -15 °C
ΔT = 4.096 °C
B.P. = 104 °C