Unit 3 - Solutions

Question 1

How to differentiate compounds?

Answer 1

based on delta chi and the bond types (ionic vs molecular)

Question 2

Compounds containing what are usually ionic?

Answer 2

metals

Question 3

Compounds containing what are usually molecular?

Answer 3

C, H, O, N, or S

if a question asks for the compound type and doesn’t mention based on delta chi then you can say that it is ionic/molecular based on this, like for NaCl

Question 4

What kind of solvents to ionic compounds dissolve in?

Answer 4

polar solvents (like H2O)

each ion is solvated and dissociates and the lattice comes apart

Question 5

what kind of solvents do molecular compounds dissolve in?

Answer 5

• polar molecules dissolve in polar solvents (H2O) and nonpolar molecules dissolve in nonpolar solvents
• like dissolves like
• molecules are also solvated by solvent molecules but do not dissociate (except acids)

Question 6

molarity

Answer 6

• moles of solute/liters of solution
• n/V
• symbol is M or c or [ ]
• units are mol/L (or M)
• can be temperature dependent because the volume of the solution may vary at different temperatures

Question 7

molality

Answer 7

• # of moles of solute/kg of solvent
• n/mass
• mass of solvent = density of solvent * volume of solvent
• in some cases, density of solvent does not equal the density of the solution and volume of solvent does not equal volume of solution
• therefore mass of solvent can be:
  mass of solvent = mass of solution - mass of solute
• units are mol/kg (or m)
• does not depend on temp

Question 8

Mole Fraction

Answer 8

• moles of solute/(moles of solute + moles of solvent)
• n(solute)/[n(solute) + n(solvent)]
• unitless
• symbol is chi x
• does not depend on temp

Question 9

Dilution

Answer 9

• process of adding additional solvent to a solution to reduce the concentration of a solution
• M1V1 = M2V2
• after dilution V2>V1 therefore M2<M1

Question 10

Acids and Bases

Answer 10

• acids are proton donor
• bases are proton acceptors

Ex:

HCl (aq) + H2O (l) -> H3O^+ + Cl^-

• free protons (H+) do not exist in aqueous solutions
• HCl is a strong acid, so it completely dissociates in water
• the H+ from the HCl gets accepted by H2O and it becomes H3O^+ and Cl^-

Question 11

7 Strong Acids in Water

Answer 11

HCl, HBr, HI, HNO3, H2SO4, HClO3, HClO4

Question 12

Weak Acids

Answer 12

• weak acids only partially dissociate in water
• Weak acids and weak bases are written as intact molecules in net ionic equations because they only partially dissociate.

Ex:
CH3CO2H -> <- H3O^+ (aq) + CH3CO2^- (aq)
- chemical equilibrium is established in the end
- some CH3CO2H (acetic acid) remain undissociated

Question 13

Monoprotic Acids

Answer 13

Have only one ionizable hydrogen atom per molecule (HCl, CH3CO2H)

Question 14

Polyprotic Acids

Answer 14

contain more than one ionizable hydrogen atom per molecule (H2SO4, H3PO4)

Question 15

Strong Bases

Answer 15

• a strong base will deprotonate the solvent molecules to completion

A^- (aq) + H2O (l) -> OH^- (aq) + HA (aq)
(generic base) (hydroxide ion)

-OH^- is a strong base in water
- Ex: NaOH, Mg(OH)2

Question 16

Neutralization Reactions

Answer 16

Reactions between acids and bases

Question 17

Reaction between strong acid and strong base

Answer 17

strong acid + strong base -> salt + solvent

Ex:
HCl (aq) + NaOH (aq) -> NaCl (aq) + H2O

Question 18

Net Ionic Equations

Answer 18

• getting rid of the spectator ions
• spectator ions function is to balance charge
• don’t get changed

Ex:
HCl+NaOH→NaCl+H2​O
ionic equation:
H+(aq) + Cl−(aq) + Na+(aq) + OH−(aq) → Na+(aq) + Cl−(aq) + H2​O(l)
spectator ions are Na⁺ and Cl⁻ because they are on both sides and don’t change
net ionic equation:
H+(aq) + OH−(aq) → H2​O(l)
.
if there are weak acids then its formula stays the same because it does not fully dissociate
.
Ex:
CH3​COOH + NaOH→ CH3​COONa + H2O
ionic equation:
CH3​COOH+ Na+ + OH− →CH3​COO− + Na+ + H2​O
Spectator ions: Na+
net ionic equation:
CH3​COOH+ OH− → CH3​COO− + H2​O

Question 19

Solubility

Answer 19

• the max amount of a compound that can dissolve in a solvent at a specific temp
• if the solubility is <0.01M then the compound is insoluble
• when a compound is insoluble or when the amount of the compound exceeds the solubility, the compound will dissociate
• use solubility rules/chart

Question 20

Precipitation Reaction

Answer 20

• if at least one product formed from a chemical reaction in water is insoluble, the reaction is a precipitation reaction
• if both products are soluble, theres no reaction

Ex:
AgNO3 and Na2CO3
forms Ag2CO3 + Na NO3
ionic equation:
2Ag+ (aq) + 2NO3- (aq) + 2Na+ (aq) + CO3^2- (aq) -> AgCO3 (s) + 2Na+ (aq) + 2NO3- (aq)
net ionic equation:
2AG+ (aq) + CO3^2- (aq) -> Ag2CO3 (s)

Question 21

Saturated Solution

Answer 21

a solution containing the max amount of solute that can dissolve at equilibrium

Question 22

Supersaturated

Answer 22

• under certain conditions, solutions may become supersaturated and dissolve more solute than in a saturated solution
• unstable

Question 23

How to calculate the mass of precipitate formed

Answer 23

1. balance equation
2. find the number of moles of the reactants
3. find the limiting reactant
4. find mass of precipitate by using the stoichiometric ratio of the limiting reactant and the precipitated product