Biochem Chapter 3: Acids, Bases and Buffers

What do bases produce in an aqueous solution?

Hydroxide ions

What is a strong acid?

A strong electrolyte, where all acid molecules ionize to H+ ions

What are some examples of a strong acid?

HCl, HBr, HNO3, H2SO4

What is a strong base?

A strong electrolyte, where all the base molecules ionize to OH- ions

What are some examples of strong bases?

NaOH, KOH, LiOH, Ca(OH)2

What is a weak acid?

A weak electrolyte, where a small percent of the molecules ionize to form H+

What is a weak base?

A weak electrolyte, where a small percent of base molecules form OH- ions

What is the purpose of the ion product constant, Kw?

To measure the tendency of water to dissociate to give H+ and OH- ions (10^-14)

What is the normal range for pH?

0-14 where 0 is acidic and 14 is basic

What is the equation for pH?

PH= -log10[H+]

What is the equation for pKa?

PKa= -log10Ka

What is the rule regarding pKa?

The smaller the value the stronger the acid

What is the purpose of the Henderson-Hasselbalch equation?

It is used to predict the properties of buffer solutions used to control pH

What does pH normally also equal?

The pKa of the weak acid

Does a strong acid usually have a smaller or larger pKa value?

A smaller pKa value

What is a titration?

An experiment in which measured amounts of base are added to an acid (or vice versa)

What is the equivalence point of a titration curve?

the point in an acid-base titration at which enough base has been added to neutralize the acid (base added=initial acid)

What is the inflection point in a titration curve?

The point where pH=pKa

If the pH is less than pKa what does that mean for H+?

H+ is bound, which means the substance is protonated

If the pH is greater than pKa what does that mean or H+?

H+ is free, which means the substance is deprotonated

What does a buffer solutions consist of?

A weak acid and its conjugate base. Example- CH3COOH and CH3COONa

What do buffer solutions do?

They tend to resist change in pH when small to moderate amounts of a strong acid/base are added

What is the overall mechanism of an action buffer?

They follow Le Chatelier’s principle; if stress is applied to a system in equilibrium, it will shift in the direction that relieves the stress

What happens to an action buffer when a H+ ion is added?

Stress is added to the reaction; H+ reacts with A- to restore equilibrium and pH doesn’t drop that much

What happens when a OH- ion is added to an action buffer?

Stress is also added; OH- reacts with H+ (forming water) which causes HA to dissociate and pH doesn’t rise that much

Which would’ve serve as a good buffer for a reaction at pH=8.0?

TRIS; pKa= 8.31

What counts as a naturally occurring buffer?

When it is in vitro (outside the living body) or in vivo (inside the living body)

What is a Zwitterion?

Compounds that have both a + and - charge

Why is a phosphate buffer important?

it is the most common and most used biological buffer