Acid base concepts

Question 1

What are nucleophiles and electrophiles?

Answer 1

Nucleophiles: Electron-rich molecules
Electrophiles: Electron poor molecules

Question 2

Is the oxygen of a water molecule a nucleophile or electrophile?

Answer 2

It is a nucleophile due to its two lone pairs of unbonded electrons

Question 3

Do strong acids and bases completely dissociate in water?

Answer 3

Yes, therefore:

[H+]=[Cl-] (using HCl as example)

Question 4

Do organic acids completely dissociate in water?

Answer 4

No they are weak acids.

Question 5

What is Ka?

Answer 5

The dissociation consant of a weak acid, the higher the value the stronger the acid.
Ka=( [H+][A-])/[HA]
where A- represents the conjugate base.

Question 6

What is pKa?

Answer 6

A logarithmic way of representing Ka.

pKa= -log(Ka), the lower the pKa the stronger the acid.

Question 7

What are buffers?

Answer 7

Solutions that resist changes in pH.

Question 8

What is the henderson-hasselbalch equation?

Answer 8

The H-H equation relates the pH of a solution containing a mixture of the two components to Ka, the concentration of the species in solution.

pH=pKa +log( [A-]/[HA] )

Question 9

What is bicarbonate buffer?

Answer 9

Regulates blood pH. Involes HCO3 and CO2.

Question 10

What is phosphate buffer?

Answer 10

Used to regulate cellular pH.

Question 11

What are protein buffers?

Answer 11

Because of the high protein concentration of cells, AA’s have a large buffering effect on pH. All AA’s have at least two ionizable groups- the amino group and carboxylate group.