Biochemistry Exam #2 Section 2.2-2.4

If you have 1 functional group you will have how many pKa's?

1 pKa

Multiple ionization groups lead to multiple pKa values. CH3COOH has how many pKa's? H2CO3 how many pKa's?

1. Is monoprotic bc it has the ability to only lose 1 proton 2. is diprotic bc it has the ability to lose 2 protons

What is the [OH-] in a solution whose pH is 3?

10^-11

The pH and pOH must always add to?

14

What is the concentration of H+ in a solution of 0.1 M NaOH?

1x10^-13 M

What is the concentration of OH- in a solution with an H+ concentration of 1.3x10^-4 M?

7.7x10^-11 M

CH3COOH--->CH3COO- + H+ which of the following above is the acid and conjugate base?

Acid - CH3COOH

__________-pH of blood < 7.4 __________-pH of blood > 7.4

Acidosis Alkalosis

True or False: 1.Buffers resist change in pH 2.At pH = pKa, there is a 50:50 mixture of acid and its anion forms of the compound (conjugate acid-base) 3.Buffering capacity of acid/anion system is greatest at pH = pKa 4.Buffering capacity is lost when the pH differs from pKa by more than 1 pH unit

All true

Study Fig. 2-18

Although the titration curves of these acids have the same shape, they are displaced along the pH axis because the three acids have different strengths. Acetic acid, with the highest Ka (lowest pKa) of the three, is the strongest of the three weak acids (loses its proton most readily); it is already half dissociated at pH 4.76. Dihydrogen phosphate loses a proton less readily, being half dissociated at pH 6.86. Ammonium ion is the weakest acid of the three and does not become half dissociated until pH 9.25

Notice that the titration curve of acetic acid has a relatively flat zone extending about 1 pH unit above and below its midpoint pH of 4.76. This zone is known as the?

Buffering region. the buffering power of the system is maximal; that is, its pH changes least.The pH at this point in the titration curve of acetic acid is equal to its pKa Note that pH is not rising along the buffering region

Does the pH scale strictly range from 0-14?

False it can go beyound 14 and beneath 0

The addition of the elements of water to the previous reaction is ________ rxn. In order to break the bond up it uses the addition of water for cleavage of a bond and only then is energy released.

Hydrolysis rxn

The extent of dissociation is determined by the acid dissociation constant ? ionization constant or acid dissociation constant?

Ka, so how far does this acid completely dissociate is what this value will tell us.

Describe the mechanism behind proton hoping.

Short "hops" of protons between a series of hydrogen-bonded water molecules result in an extremely rapid net movement of a proton over a long distance. As a hydronium ion (upper left) gives up a proton, a water molecule some distance away (bottom) acquires one, becoming a hydronium ion. Proton hopping is much faster than true diffusion and explains the remarkably high ionic mobility of H+ ions compared with other monovalent cations such as Na+ and K+.

________ and ______ are completely ionized/ dissociate in dilute aqueous solutions. Examples include HCl, HNO3, H2SO4, NaOH, KOH.

Stong acids and bases

Study Fig 2-19

The system is capable of absorbing either H+ or OH- through the reversibility of the dissociation of acetic acid. The proton donor, acetic acid (HAc), contains a reserve of bound H+, which can be released to neutralize an addition of OH- to the system, forming H2O. This happens because the product [H+][OH-] transiently exceeds Kw (1X10^-14M2). The equilibrium quickly adjusts to restore the product to 1x10^-14 M2 (at 25 8C), thus transiently reducing the concentration of H+. But now the quotient [H+][Ac2]/[HAc] is less than Ka, so HAc dissociates further to restore equilibrium.

A _________ system consists of a weak acid (the proton donor) and its conjugate base (the proton acceptor).

a buffer system

Water molecules have a slight tendency to undergo reversible ionization to yield a?

a hydrogen proton and a hydroxide ion

Titration is used to determine the amount of an ________ in a given solution. A measured volume of the acid is titrated with a solution of a strong base, usually sodium hydroxide (NaOH), of known concentration.

acid

may be defined as a proton donor that have the ability to release protons?

acid

is a molecule that can accept a proton?

base

________ are aqueous systems that tend to resist changes in pH when small amounts of acid (H+) or base (OH-) are added.

buffers

The formation of ATP from ADP and inorganic phosphate is an example of a __________ reaction in which water is eliminated

condensation rxn

A proton donor and its corresponding proton accepted make up a?

conjugate acid-base pair

At the midpoint of the titration curve, the concentrations of the proton donor and proton acceptor are ______ and the pH at that point it numerically equal to the ______.

equal pKa

Stronger acids will have a smaller or larger ionization constant? Where as weaker acids will have a smaller or larger ionization constant?

larger smaller

pH is inversely related so if proton [ ] is high the pH is _____?

low

The stronger the tendency to dissociate a proton, the stronger is the acid and the lower or higher its pKa? Weaker the acid the lower or higher its pka?

lower higher

When there are exactly equal concentrations of H+ and OH- as in pure water, the solution is said to be at ?

neutral pH

Water and carbon dioxide are formed by the _________ of fuels such as glucose?

oxidation

The total hydrogen ion concentration from all sources is experimentally measurable and is expressed as the ______ of a solution.

pH

What is the Henderson-Hasselbalch equation?

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

___________ is a convenient means of designating the concentration of H+ (and thus of OH-) in any aqueous solution in the range between 1.0 M H+ and 1.0 M OH-.

pH scale

A plot of pH against the amount of NaOH added (a titration curve), reveals the ______ of a weak acid.

pKa

Also, included are values of ______ , which is analogous to pH

pKa

______ refers to dissociation of a proton from a particular functional group.

pKa

________ and __________ are not completely ionized/dissociated when dissolved in water.

weak acids and bases

Water molecules ionize strongly or weakly?

weakly

Can pH be negative?

yes