Acid Base Flashcards
Define a Brønsted-Lowry acid. Why is it called so? What’s the equation
It’s a proton donor.
It’s called so as when acid dissolves in water it releases H+ ions.
H+ ions don’t exist in their own in water, so they form hydroxonium ions H3O+ and this is what makes the solution acidic
- HA(acid)(aq)+H2O(l)—> H3O+(aq)+A-(aq)
Define a Brønsted-Lowry base. Why are they called so? Write the equation
They are proton acceptors.
When they dissolve in water they react with the H+ ions to form OH (hydroxide ions)
B(aq)(base)+H2O->BH+(aq)+OH-(aq)
What type of reaction occurs when acid and base reacts with water
Reversible reaction.
Acids - HA + H2O <-> H3O+ + A-
Base - B + H2O <-> BH+ + OH-
How does strong acid/base and weak acid/base react? Give examples with equation
Strong acid/base dissociate or ionise almost completely into H+/OH- (Forward reaction is favoured - lots of H+/OH- produced)
Strong base (NaOH, KOH, NaOH<—>Na+ + OH-)
Strong acid (HCl, H2SO4, HCl <->H+ + Cl-)
Weak acid/base dissociate poorly. Backward reaction is favoured so not many H+/OH- ions are produced
(Weak acid (Ethanoic acid and other carboxylic acids, CH3COOH <-> CH3COO- + H+)
Weak base(Ammonia -it depends on water to produce oh- ions, NH3 + H2O <-> NH4+ + OH-)
What is a conjugate acid
Any species that has gained a proton is the conjugate acid
What is a conjugate base
Any species that has lost a proton
Equation of Brønsted-Lowry Lord acid and base reaction. Which are the 2 conjugate pairs (3)
When acid and base react with each other, protons are exchanged.
HA + B <-> BH+ + A-
Pair 1 - HA(conjugate acid) A- (Conjugate base)
Pair 2 - BH+ (conjugate acid) B (Conjugate base)
How does water react to form conjugate acid and base
Water reacts with acids to form H3O+( Conjugate acid) HA(aq) +H2O (l) <-> H3O+(aq) + A-(aq)
Reacts with base to form a conjugate base OH- (B(aq) + H2O (l) <-> BH+(aq) + OH-(aq))
How does water behave when acid is added
Water behaves as a base when acid is added. It accepts the protons to form hydroxonium ions
How do acid and base react and what is formed
Acid and base reaction -> Neutralisation reaction (H+(aq)+ OH-(aq)<-> H2O(l)) produces salt which are pH neutral.
[H+] = [OH-]
Salts are formed from the metal from the base ( or ammonium ions) and non metal of acid (other than H+)
What’s different with ammonia
Ammonia doesn’t produce oh- ions directly. It reacts with water first and accepts a proton to produce NH4+ and OH- ions.
Ammonia reacts with acids to make ammonium salts but no water.
Define standard enthalpy change of neutralisation. Is it exo or endothermic? And why
Enthalpy change that accompanies a reaction of an acid and base under standard conditions, to produce 1 mole of water.
Neutralisation is always exothermic so enthalpy change of neutralisation is always negative
Enthalpy of neutralisation with weak acids and base
Weak acids and base dissociate weakly and so the OH- and H+ ions are used up quickly and so they are constantly dissociating to replace the ones used.
So 2 types of enthalpy is involved - Enthalpy of dissociation, enthalpy when oh- and h+ react
Enthalpy of dissociation varies depending on the acid and base used. This means enthalpy of neutralisation of weak acids and bases varies too
Enthalpy of neutralisation with strong acid and bases
Strong acids and base dissociate fully and so only enthalpy of oh- and h+ is involved. It doesn’t involve enthalpy of dissociation as they fully dissociate.
As a result enthalpy of neutralisation is quite similar for all reactions of strong acids and base
What is pH? What’s its scale range. What’s the equation
pH is a logarithmic scale that measures the concentration of H+ ions in solution.
Range 0-14 (0 is very acidic, 7 is neutral, 14 is very basic)
pH=-log10[H+]
