Acids and Bases Flashcards
What is a bronstead acid?
A bronstead acid is a molecule that can donate a proton to a base e.g CH3COO- + H+
What is a bronstead base?
What is a base?
A molecule that can pick up a proton
What is an acid?
Any molecule that contains H joined to a more electronegative atom
What is the pH equation?
pH= -log [H3O+]
What is the equation for [H3O+]?
[H3O+] = 10-pH
What is the Ka equation?
Ka = [A-][H3O+] / [HA]
What does a high pKa mean?
A high pKa means that it is a weak acid. A weak acid has a strong conjugate base. A pKa can go into negative digits.
What makes a strong acid?
- More positive or less negative charge
- Charge stabilisation by;
- Inductive effects
- Delocalisation
What does the following tell us?
- pH < pKa
- pH = pKa
- pH > pKa
When pH is less than pKa there is more acid then base with pH equals pKa they are equal when pH is greater than pKa there is more conjugate base then acid
What is speciation?
Speciation is the amount of each species in solution when they are at different forms. This occurs different pH levels depending on the pKa of each acid and conjugate base
What is interesting about amino acids at pH 7?
The form a zwitterion which is whern the CHOO- group has lost an H but the NH3+ has an extra charge so the whole molecule has no net charge however both of the side chains are charged
What changes on an amino acid between pH 7 and pH 1?
At pH 7 there is a zwitterion where as pH 1 the COO- group has an H = COOH therefore the whole amino acid is +ve charged
What changes on an amino acid between pH 7 and pH 12?
At pH 7 a zwitterion forms however at pH 12 the NH3 group has lost an H and is no longer +ve this means that the whole molecule is now has a -ve charge
What is one assumption we make when a strong acid reacts with water?
Only the strong acids contributes to the H30+ concentration this is not true when the calculated pH is > 6