U6 acids and bases

Arrhenius theory is based on…

Based on release of H+ or OH- ions in solution, as it doesn't explain all acid and bases (not IB)

• acids: increase hydrogen ion (H⁺) concentration in water

• bases: hydroxide ion (OH⁻) concentration in water

Bronsted lowry theory is based on…

Based on the transfer of protons, H+ ions between reactants

Lewis theory is based on…

Based on the transfer of electron pairs between reactants

Bronsted lowry acids →

donate proton to another reactant

Bronsted lowry bases →

accept proton to another reactant

meaning of Monoprotic, diprotic, tripotic

number of protons they can donate in an acid-base rxn

Amphiprotic means..

they’re species that can donate and accept a proton

e.g. H2O, HCO3-, NH3

relationship of acidity and H+ conc to pH

• As pH increase

  • the solution is less acidic, more basic

  • The solution has higher conc of H+ than OH-

• As pH decrease

  • the solution is more acidic, less basic

  • The solution has lower conc of H+ than OH-

when is pH neutral

at 25C

pH = 7

what is pH

• Measurement of the acidity of a solution

• measurement of H+ (or H3O+) conc in a solution

why is pH a log scale

pH is a log scale, which is more useful in representing very large or very small numbers a simpler numbers

A ___ unit change in pH is a ______ change in [H+]

A ONE unit change in pH is a TEN fold change in [H+]

e.g. pH change from 3 to 5, [H+] is 100 more basic

state 3 Experimental methods of measuring pH

1. pH sensor gives a precise value

2. pH indicator paper gives an estimated value

3. Universal indicator gives an estimated value

what does Dissociation constant for water, Kw represent

Aka water equilibrium expression

The ratio of H+ and OH- in an aq solution

At 25C, Kw is 1x10^-14

Strength acids and bases is determined by

the extent of dissociation (or ionization)

compare and contrast strong acid/base VS weak acid/base

• strong dissociates completely, weak dissociates partially

• strong is irreversible, weak is an equilibrium (back and fourth rxn)

• strong has high H+ conc, weak has low H+ conc

• all are electricity conductors

state the 5 strong acids

HCL - hydrochloric acid

HBR - hydrobromic acid

HI - hydroiodic acid

H2SO4 - sulfuric acid

HNO3 - nitric acid

state the 3 strong bases

LiOH - lithium hydroxide

NaOH - sodium hydroxide

KOH - potassium hydroxide

what are the weak acids?

• Carboxylic acids

• H2CO3, HsPO4, H2SO3, HCN, HNO2, and more

• Other complex ions (e.g. [Al(H2O)6]3+)

what are the weak bases?

• Amines, 

• NH3, 

• N2H4

general periodic pt trends of acids to bases

left (strong bases) → right (strong acids)

gen eq of metal oxide + water

e.g. MgO + H2O

→ metal hydroxide

→ Mg (OH)2

gen eq of non metal oxide + water

e.g. CO2 + H2O

→ oxyacid (comme sulfuric acid and nitric acid)

→ H2CO3

neutral rain VS acid rain pH

neutral: 5.6

acid: 4-5

Outline acid deposition using SOx and NOx

outline ocean acidification using CO2

pH of ocean changes

• 1950: 8.15

• 2020: 8.05

reative metal + water

→ metal hydroxide + H2

metal oxide + water

→ metal hydroxide

non metal oxide + water

→ oxyacid

metal + acid

→ salt + H2

metal oxide + acid

→ salt + water (neutralisation)

metal hydroxide + acid

→ salt + water (neutralisation)

metal carbonate + acid

→ salt + water + CO2 (neutralisation)

acid + amine

→ salt

what are neutralisation reactions?

• When acid and base form salt and water

• Usually exothermic

• The proton of the acid reacts with the hydroxide of the base to form water:

• The spectator ions which are not involved in the formation of water, form the salt