Buffers 4

What are buffer solutions used for?(3)

Calibration of pH meters

Culture bacteria

Controlling pH of solutions for chemical reactions

What does adding HCl or NaOH change pH of water?

Water has no mechanisms to neutralise incoming acidic or basic impurities

What are buffers composed of either?

A weak acid plus a salt of the acid

A weak base plus a salt of the base

How does a buffer stabilise the pH of a solution?

By providing a source or sink for protons

How is a weak conjugate acid formed?

By the strong base accepting a proton

When do buffers work best?

At a pH = pKa of acid or base from which they are made

What is the acid?

The species with more hydrogens

What is the buffer capacity (β)?

Number of moles of strong monobasic acid required to produce an increase or decrease of 1 unit on pH scale

When can a buffer with high capacity maintain its buffering action?

After addition of more strong acid or base than one with a small capacity

When is a buffer high capacity?

When there is 10% more base than acid otherwise the base gets used up quickly

When is a buffer low capacity?

When there is 10% more acid than base otherwise the acid gets used up quickly

Bloodstream and intracellular fluid buffered to pH of 7.4 by action of three main buffers:

Dissolved CO2

Dihydrogen phosphate H2PO4-

Protein macromolecules

All amino acids are chiral except?

Glycine

What does chiral mean?

One that is not identical to its mirror image

What are zwitterion properties?

Dipolar ion

Makes amino acids very polar and very soluble in water

Amphiprotic

In solution both function groups ionise to form salt

What is the isoelectric point?

The average of the 2 pKa values on either side of the zwitterion