Acid-Bases Flashcards
Brønsted-Lowry definition of an acid
A substance that donates a proton to a different substance
Brønsted-Lowry definition of a base
A substance that accepts a proton (H+ ion)
What can acids or bases be?
Either strong or weak
Strong acids
A substance that donates a proton and fully dissociates when mixed with water
So all H+ ions are released
How can we represent a strong acid?
HA
Dissociation of strong acid when mixed with water? Simple generic equation
HA + aq ——> H⁺ + A-
Dissociation of a strong acid when mixed in water? - more detailed generic equation
HA + H2O ——> H₃O⁺ + A-
Is the dissociation of strong acids in water under equilibrium?
Yes but very strongly favours the forward reaction so the concentration of H+ ions is high- lots produced
Dissociation of strong acid in water - what do the products form in neutralisation?
The A- (non metal in acid) will form part of the salt
The H+ ions will be accepted by the base to form water (neutralisation)
What is H₃O⁺?
A hydronium ion, that H+ ions react with water in the aqueous solution to form
Strong base
A substance that accepts protons and fully dissociates into its ions to when mixed with water
How can we represent a strong base?
B
Dissociation of strong bases in water - simple generic equation
B + H2O ——> BH⁺ + OH-
What is happening in the dissociation of a strong base in water?
OH- ions in the base are released
As well as accepting a H+ ion from water so the rest of the water can form OH- to form the BH+ (base accepts proton)
Is dissociation of a strong base a reversible reaction?
Barely because POE is so far to the right that a high conc of OH- ions are released
Weak acids
A proton donor that only partially dissociates when mixed with water into its ions
Not all H+ ions are released
Examples of weak acids
All carboxylic acids
Dissociation of weak acid when mixed with water - more detailed generic equation
RCOOH + H2O <——> CH3COO- + H3O+
Dissociation of weak acid when mixed with water - simple generic equation
RCOOH <——> RCOO- + H+
Is the dissociation of a weak acid in water a reversible reaction?
Yes, which lies heavily to the left so low conc of H+ ions due to only partial dissociation
Weak bases
A proton acceptor that only partially dissociates when mixed with water
Examples of weak bases
Ammonia
dissociation of ammonia (weak base) when mixed with water
NH3 + H2O <——> NH4+ + OH-
How is OH- ions released from dissociation of NH3 in water if no OH ion is in NH3?
Relies on accepting H+ ions from the water, to form an ammonium ion
And the rest of the molecule exists as OH-
In a neutralisation reaction, what occurs?
The H+ and OH- ions released in dissociation of acid/base respectively in water react together to form water
The negative ion from acid + positive ion from base ——> salt
Acid base conjugate pairs
In a reaction, the acid will donate a H+ and what’s left of it = the conjugate base
In a reaction, the base will accept a H+ ion and what is formed is the conjugate acid
Why is what is left of the acid, form a conjugate base?
Because if the reaction was reversed, then the conjugate base acts as a base and accepts a H+ ion because it can to form an acid
Why is what the base forms, the conjugate acid?
Because the base accepts a H+ ion to form an acid
Because this H+ ion can be donated (an acid) if the reaction was reversed
Does acid-base conjugation also refer to mixing acids/bases in water?
Yes
Acid-base conjugation in dissociation of acid in water
Water acts as a base where it accepts the H+ ions from the acid to form H3O+ ions (the conjugate acid)
Acid which loses H+ ions, it’s anion will form the conjugate base
What does water act as in the dissociation of strong acid in water?
The base to accept the H+ ion to form H3O+
Acid base conjugation in dissociation of base in water
The water acts as the acid because it donates the H+ ion to the base in order to form OH- (the conjugate base)
The base accepts the H+ ion to form the conjugate acid
What does water act as in the dissociation of a base in water?
The acid
