2.4 Strong and Weak Acids and Bases and Their Salts Flashcards
Strong acids and weak acids
STRONG:
Hydrochloric acid
Sulphuric acid
Nitric acid
Phosphoric acid
WEAK:
Everything else
Carboxylic acids
Strong bases and weak bases
STRONG:
Group 1 (and some group 2)
WEAK:
Ammonia
Amines
The greater the number of H+ ions, …
The lower the pH and the greater the conductivity
What means the lower pH and the greater the conductivity
More H+
The greater the OH-, ….
The higher the pH and the greater the conductivity
Weak acids and bases are _________ in dilute solution.
Partially ionised
___________ are only partially ionised in dilute solution.
Weak acids and bases
Weak acids can neutralise the same amount of an alkali as a strong acid
Although they have fewer H+ ions, as soon as they are used up the equilibrium will shift to the right to make more
In the end, a weak acid can provide the same amount of H+ ions as a strong acid.
Strong acid strong base salt
Both fully dissociate in water
They will stay dissociated and do not reform the parent acid or base
Therefore, the water is unaffected
pH remains 7
Both fully dissociate in water
They will stay dissociated and do not reform the parent acid or base
Therefore, the water is unaffected
pH remains 7
Strong acid strong base salt
Strong acid weak base salt
Strong acid stays fully dissociated in water and thus doesn’t affect the pH of the salt
The weak base reforms its equilibrium by removing hydroxide ions from the water equilibrium.
More water molecules dissociate and the water equilibrium shifts to the right to replace hydroxide ions.
This results in excess hydrogen ions.
H+ > OH-
Thus, the pH of the salt is acidic
Weak acid strong base
Strong base stays fully dissociated in water and thus doesn’t affect the pH of the salt
The weak acid reforms its equilibrium by removing hydroxide ions from the water equilibrium.
More water molecules dissociate and the water equilibrium shifts to the right to replace hydrogen ions.
This results in excess hydroxide ions.
H+ < OH-
Thus, the pH of the salt is alkaline
Strong base stays fully dissociated in water and thus doesn’t affect the pH of the salt
The weak acid reforms its equilibrium by removing hydroxide ions from the water equilibrium.
More water molecules dissociate and the water equilibrium shifts to the right to replace hydrogen ions.
This results in excess hydroxide ions.
H+ < OH-
Thus, the pH of the salt is alkaline
Strong base weak acid
Acid is defined as having
H+ > OH-
What does H+ > OH- mean for acids
They can act as protein donors, donating H+
The resulting species is known as a conjugate base
The donated H+ is known as a conjugate acid
