TEST 5 (Acids and Bases: Nature, Strength, Calculations and Salt Soltions Flashcards
Properties of Acids
Sour
Watery feeling
Low pH
Reacts with metals to form hydrogen gas and a salt
Reacts with a base to form a salt and water
Properties of Bases
Sour Slippery feeling High pH Non-reactive with metals Reacts with acid to form a salt and water
Arrhenius Theory
Acid –> Produces H+
Base –> Produces OH-
Problem with Arrhenius theory
Doesn’t argee with NH3 and weak bases
Bronsted Lowry Theory
Acid –> hydrogen ion donor
Base –> hydrogen ion acceptor
Conjugate Base
Forms from acids
Conjugate Acid
Forms from bases
Amphiprotic Substances
Can behave as an acid or base
Acid Ionization Constant
Ka
Equilibrium constant for the ionization of an acid
High Ka
Low pH
High concentration of products [H]
Strong Acid
Low Ka
High pH
Low concentration of [H]
Weak acid
Strong Acid
Large Ka
Equilibrium far to the right
[H] ~ [HA]
Weak Acid
Small Ka
Equilibrium far to the left
[H] «_space;[HA]
Acids and their Conjugate Base
Strong Acid –> less likely to form acid from conjugate base (weak cb)
Weak Acid –> more likely to form acid from conjugate base (strong cb)
General Acid –> same strength as conjugate base
Kb
Base dissociation constant
High Kb –> strong base
Low Kb –> weak base
Water is an acid & a base
Autoionization of water explains Kw (1.0 x 10-14)
Kw
= (Ka)(Kb)
pH
-log[H]
pOH
-log[OH]
pH < 7
Acid
pH > 7
Base
pH = 7
Neutral
How do we measure pH?
pH paper
acid-base indicators
pH meter
Sig Figs
2 sig figs in log for concentration –> 2 digits after decimal in pH
Strong Acid Calculations
Ionize completely in water
Only BCE needed using ratios
Weak Acid Calculations
Don’t completely ionize
(Use BCE and ICE chart)
Could also use Percentage Ionization
Percentage Ionization
Concentration of ionized acid/ Initial concentration of acid x 100%
(H/HA x 100%)
Monoprotic Acid
Will donate a singular acidic proton
Polyprotic Acid
Can donate more than 1 acidic proton
Diprotic and Triprotic
Steps for Polyprotic Acids
Will donate 1 ion per step
There will be a different Ka value for each step –> (Ka will get smaller because it isn’t favourable to lose another proton)
Basic Solutions
Similar to acid calculations but use pOH, Kb, [OH]
Neutral Salt Solution
When salt solution ions would make both strong acid and base –> they wont want to ionize/dissociate –> wont affect the pH very much
Basic Salt Solutions
When anion would form strong conjugate base
BCE will contain water
Acidic Salt Solution
When cation would form a strong conjugate acid
BCE with cation as only reactant
