Acid-Base Equilibria Flashcards
What effects do alkyl groups have on carboxylic acids?
They push electrons away from themselves –> small amount of -ve charge builds up on the -COO- group –> ion less stable, weakening the acid.
Why does a strong base have a weak conjugate acid?
Eqm. lies very far to the LEFT (very strong attraction for H+). Consequently true that very few HA dissociate in the backward reaction –> HA very weak.
when should the indicator change colour during a titration?
Over the VERTICAL section of the pH titration curve.
What do buffer solutions do?
Resist changes in pH even when small amounts of acid or alkali are added to them.
How does diluting a buffer solution affect the pH?
No effect as acid:base ratio doesn’t change.
what can you say about the ionisation of water?
it is endothermic.
what effect does diluting by a factor of ten have on a strong and a weak acid?
increases by one pH unit / increases by less than one unit as dissociation increases.
What can you say about a buffer solution if [acid] and [salt] are the same?
pH of buffer = pKa of acid.
when a weak acid is neutralised is the end-point above or below 7?
above.
In what case would the equivalence point be 7 for a weak acid and weak base titration?
If the dissociation constants for the weak acid and base are approximately equal.
What is Kw?
Kw is the ionic product for water.
What happens to the pH of water at higher temperatures?
It falls but water does NOT become more acidic!
why are buffers used in foods?
they prevent deterioration due to pH changes caused by bacterial or fungal activity.
