Chem 162 Actual Exam Questions and
Verified Answers
Which substances are most likely to undergo dissolution in water?
octane, C8H18
lithium chloride, LiCl
potassium bromide, KBr
sodium bromide, NaBr
benzene, C6H6
lithium chloride, LiCl
potassium bromide, KBr
sodium bromide, NaBr
Define entropy vs enthalpy
entropy - Tendency for energy to spread out (disperse) when its not retrained from doing so in
the absence of IMF
enthalpy - measure of heat change under constant pressure and temp (used in energetics)
What is henry's law? units?
relationship that shows how solubility of a gas in a liquid is affected by pressure
solubility (M) = P (atm) * k (M/atm)
solubility?
,amount of substance that dissolves in given amount of solvent
Air is a mixture of gases that is about 78.0%% N2 by volume. When air is at standard pressure and 25.0 ∘C, the N2
component will dissolve in water with a solubility of 4.88×10−4 M. What is the value of Henry's law constant for N2 under
these conditions?
As a scuba diver descends under water, the pressure increases. At a total air pressure of 2.93 atm and a temperature
of 25.0 ∘C, what is the solubility of N2 in a diver's blood? [Use the value of the Henry's law constant k calculated in
Part A, 6.26×10−4mol/(L⋅atm).] Assume that the composition of the air in the tank is the same as on land and that all
of the dissolved nitrogen remains in the blood.
k = 6.26e−4 mol/L⋅atm
solubility = 1.43e−3 mol/L
Saturated vs Unsaturated
Unsaturated solution - solution containing less than equilibrium amount of solute
Saturated solution - amount of dissolved solute is equal to the solubility of the solute
spontaneous solution? ex.?
happens with no external influence
Ex. Ball rolling down hill
ideal solution?
solute molecules randomly dispersed through the solvent
What factors affect solubility? relationships?
Molecular structure "like-dissolves like"
polar and polar have high solubility
, non- and polar have lower solubility
Pressure
increases solubility
Temp
decreases with high temp. (gas), increases with high temp (solid)
Hydrophilic vs. Hydrophobic, 3 examples
Hydrophilic - Water-loving, Polar
Hydrophobic - Water-hating, Non-polar
1. Sodium sterate (soaps/detergents)
Separates into Na with water
C chain are hydrophobic
Hydrophobic tail sticks in grease
Hydrophilic end solvated by water
Ex. Cell membranes
Two chains of C and one hydrophilic end
Self assemble into membrane
Tails are attracted to each other, heads want to be far away (towards outside of cell)
Ex. Virus particle structure
DNA/RNA Protein coat (capsid) in a liquid envelope
solubility and pressure relationship? when does this apply?
Increasing pressure -> increase solubility
ex. CO2 staying dissolved in solution when can is closed
Verified Answers
Which substances are most likely to undergo dissolution in water?
octane, C8H18
lithium chloride, LiCl
potassium bromide, KBr
sodium bromide, NaBr
benzene, C6H6
lithium chloride, LiCl
potassium bromide, KBr
sodium bromide, NaBr
Define entropy vs enthalpy
entropy - Tendency for energy to spread out (disperse) when its not retrained from doing so in
the absence of IMF
enthalpy - measure of heat change under constant pressure and temp (used in energetics)
What is henry's law? units?
relationship that shows how solubility of a gas in a liquid is affected by pressure
solubility (M) = P (atm) * k (M/atm)
solubility?
,amount of substance that dissolves in given amount of solvent
Air is a mixture of gases that is about 78.0%% N2 by volume. When air is at standard pressure and 25.0 ∘C, the N2
component will dissolve in water with a solubility of 4.88×10−4 M. What is the value of Henry's law constant for N2 under
these conditions?
As a scuba diver descends under water, the pressure increases. At a total air pressure of 2.93 atm and a temperature
of 25.0 ∘C, what is the solubility of N2 in a diver's blood? [Use the value of the Henry's law constant k calculated in
Part A, 6.26×10−4mol/(L⋅atm).] Assume that the composition of the air in the tank is the same as on land and that all
of the dissolved nitrogen remains in the blood.
k = 6.26e−4 mol/L⋅atm
solubility = 1.43e−3 mol/L
Saturated vs Unsaturated
Unsaturated solution - solution containing less than equilibrium amount of solute
Saturated solution - amount of dissolved solute is equal to the solubility of the solute
spontaneous solution? ex.?
happens with no external influence
Ex. Ball rolling down hill
ideal solution?
solute molecules randomly dispersed through the solvent
What factors affect solubility? relationships?
Molecular structure "like-dissolves like"
polar and polar have high solubility
, non- and polar have lower solubility
Pressure
increases solubility
Temp
decreases with high temp. (gas), increases with high temp (solid)
Hydrophilic vs. Hydrophobic, 3 examples
Hydrophilic - Water-loving, Polar
Hydrophobic - Water-hating, Non-polar
1. Sodium sterate (soaps/detergents)
Separates into Na with water
C chain are hydrophobic
Hydrophobic tail sticks in grease
Hydrophilic end solvated by water
Ex. Cell membranes
Two chains of C and one hydrophilic end
Self assemble into membrane
Tails are attracted to each other, heads want to be far away (towards outside of cell)
Ex. Virus particle structure
DNA/RNA Protein coat (capsid) in a liquid envelope
solubility and pressure relationship? when does this apply?
Increasing pressure -> increase solubility
ex. CO2 staying dissolved in solution when can is closed
