Lecture 5: Solutions

Question 1

Solutions: solvent and solute

Answer 1

1. In a solution: solvent is the compound with more and solute is the compound with less

Question 2

3 types of solutions

Answer 2

1. Ideal: formed when mixed compounds have similar size and intermolecular bonding properties
2. Ideally dilute: solute molecules are completely separated by solvent molecules so they dont interact
3. Nonideal: neither ideal or ideally dilute

Question 3

Colloids

Answer 3

1. Colloid is like a solution with larger solute particles
2. A colloid system can be a combination of phases: aerosols, foam, emulsion, sol etc.

Question 4

Molarity (M)

Answer 4

Molarity=M=(Moles (solute)/Volume (solution))=n/L

Question 5

Molality (m)

Answer 5

1. Molality=m=(Moles(solute))/(Kg(solvent))=n/Kg

Question 6

Mass percentage

Answer 6

1. Mass %= (Kg solute/Kg total solution) x 100

Question 7

Parts per million

Answer 7

1. Ppm=(Kg solute/ Kg total solution) x 10^6

Question 8

Dissolution

Answer 8

1. When a solute is mixed with solvent and dissolves
   1a. Solvent molecules surround solute molecules forming a solvation shell (if water called hydration shell)
   1b. In protein folding this is driven via he hydrophobic effect
2. “Like dissolves like”
3. Opposite process is called precipitation

Question 9

Electrolytes

Answer 9

1. Ions in aqueous solution
   1a. Strong electrolytes (strong ionic molecules) conduct electricity very well and have many ions

Question 10

Process of dissolution

Answer 10

1. Step 1 (endothermic): break intermolecular bonds between solute molecules
2. Step 2 (endothermic): break intermolecular bonds between solvent molecules
3. Step 3 (exothermic): form intermolecular bonds between solvent and solute molecules

Question 11

Solubility (s)

Answer 11

1. Represents a solutes tendency to dissolve in a solvent

Question 12

Solubility product (Ksp)

Answer 12

1. Doesn’t include solids!

Question 13

Vapour pressure of a pure liquid

Answer 13

1. Vapour pressure of a substance is a function of its intermolecular bonds and its kinetic energy

Question 14

Vapour pressure of a solution

Answer 14

1. Raoult’s law: Pv=XaPa
   1a. Xa=mole fraction of liquid and Pa=vapour pressure of liquid

Question 15

Extra

Question 16

Solubility factors: temperature

Answer 16

1. As temperature increases, solubility of salt increases

Question 17

Solubility factors: pressure effects

Answer 17

1. Shown via Henry’s law: s=kPv
   1a. S=solubility, k=henrys constant, Pv=vapor partial pressure
2. Shows that solubility of gas is proportional to its vapour partial pressure

Question 18

Solubility guidelines

Answer 18

1. Compounds w water solubilities of less than 0.01 mol/L are insoluble
2. Nearly all ionic compounds are soluble

Question 19

Qsp vs Ksp

Answer 19

1. Qsp=Ksp: solution is saturated & at equilibrium so no precipitate will form
2. Qsp<Ksp: solution is unsaturated so no precipitate will dorm
3. Qsp>Ksp: solution is supersaturated so precipitate will form