Solution Chemistry

Question 1

What is moles solute?

Answer 1

L of solution.

Question 2

What is moles of solute?

Answer 2

Kg of solvent.

Question 3

What is an ideal solution?

Answer 3

• An ideal solution or ideal mixture is a
solution in which the enthalpy of
solution (ΔHsolution) is zero.

Question 4

What determines the gibbs energy of mixing for ideal solution?

Answer 4

entropy of mixing ( ΔSsolution ).

Question 5

What are the main features of an ideal solution?

Answer 5

• The enthalpy of mixing of two components is zero.
• The forces of attraction between solvent and solute are exactly the same as between the original solvent molecules
• The volume of the mixing is equal to zero that is, ΔV = 0.
• Obey Raoult’s law at all concentrations and temperatures

Question 6

What is Rault’s law?

Answer 6

The vapor pressure of a solvent above a solution is
equal to the vapor pressure of the pure solvent at the same temperature scaled by the mole fraction of the solvent present.

Question 7

What is the formula of Rault’s law?

Answer 7

P solution= χsolvent Po solvent

where Po solvent is the vapor pressure of pure solvent and χsolvent is its mole fraction in the solution.

Question 8

What are non-ideal solutions?

Answer 8

The solutions which don’t obey
Raoult’s law at every range of
concentration and at all temperatures
are non-ideal solutions.

Question 9

What are features of non-ideal solutions?

Answer 9

• The enthalpy of mixing of two components is not zero.
• The forces of attraction between solvent and solute are not
the same as between the original solvent molecules
• The volume of the mixing is not equal to zero that is, ΔV ≠ 0.
there will be some expansion or contraction in the dissolution of liquids.
• Do not obey Raoult’s law.

Question 10

What are the types of non-ideal solution?

Answer 10

Solutions that show positive deviation from Rault’s law and solutions that show negative deviation from Rault’s law.

Question 11

What are features of positive non-ideal solutions?

Answer 11

1. The enthalpy of mixing is positive (endothermic).
2. The solute-solvent forces of attraction is weaker than
   solute-solute and solvent-solvent interaction.
3. The volume of mixing is positive that is, ΔV > 0 as the
   volume expands on the dissolution of components A and B.
4. PA > χA PoA

Question 12

What are features of negative non-ideal solutions?

Answer 12

1. The enthalpy of mixing is negative (exothermic).
2. The solute-solvent forces of attraction is greater than
   solute-solute and solvent-solvent interaction.
3. The volume of mixing is negative, that is ΔV < 0, as the
   volume decreases on the dissolution of components A and B.
4. PA < χA PoA

Question 13

What is boiling point?

Answer 13

The boiling point is the temperature at which the vapor pressure of a liquid is equal to the external pressure.

Question 14

What is freezing point?

Answer 14

Freezing point is reached when the chemical potential of the liquid solvent reaches that of the solid solvent (energetically equivalent). Chemical potential is the
molar Gibb’s energy that one mole of solvent is able to contribute to a mixture

Question 15

What is vapor pressure?

Answer 15

The pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed container

Question 16

What is osmotic pressure?

Answer 16

The osmotic pressure of a solution is the pressure difference needed to stop the flow of solvent across a semipermeable membrane.

Question 17

What are colligative properties?

Answer 17

Colligative properties are the
physical changes that result from
adding solute to a solvent.
Colligative Properties depend on the
quantity solute particles present as
well as the solvent amount, but they
do NOT depend on the type of
solute particles, although do
depend on the type of solvent.

Question 18

What is the role of solute in colligative properties?

Answer 18

Solute must not contribute to the
vapor pressure of the solution.

• Solute must remain suspended in
the solution even during phase
changes.

Question 19

What are examples of colligative properties?

Answer 19

Freezing
point
depression

Boiling point
elevation

Vapor
pressure
lowering

Osmotic
Pressure

Question 20

What is freezing point depression?

Answer 20

The freezing points of
solutions are all lower than that of
the pure solvent and is directly
proportional to the molality of the
solute.

Question 21

What is the formula of freezing point depression?

Answer 21

ΔTf = Tf(solution) − Tf(solvent) = − Kf × m

where ΔTf
is the freezing point depression,
m is the solute molality, Kf
is the freezing
point depression constant.

Question 22

What is boiling point elevation?

Answer 22

The boiling points of solutions are
all higher than that of the pure
solvent.

Question 23

What is formula for boiling point elevation?

Answer 23

ΔTb= Tb(solution) − Tb (solvent) = Kb × m

where ΔTb
is the boiling point elevation, m
is the solute molality, Kb
is the boiling point
elevation constant.

Question 24

What is vapor pressure lowering?

Answer 24

The vapor pressure of a solvent in a
solution is always lower than the
vapor pressure of the pure solvent.

Question 25

What is osmotic pressure?

Answer 25

The osmotic pressure of a solution is
the pressure difference needed to
stop the flow of solvent across a
semipermeable membrane.

Question 26

What is formula for osmotic pressure?

Answer 26

Π = MRT

where Π is the osmotic pressure, R
is the ideal gas constant, T is the
temperature in Kelvin, M is molar
concentration of solute

Question 27

What are anomalous colligative properties?

Answer 27

Anomalous colligative properties
are colligative properties that
deviate from the norm.

Question 28

Who discovered anomalous colligative properties?

Answer 28

Jacobus Van’t Hoff

Question 29

What is the formula for i (colligative properties)

Answer 29

Observed property / theoretical property