Acid Base Chemistry

Question 1

Any molecule that donates H+ in aqueous solution?

Answer 1

Acid

Question 2

Any molecule that accepts H+ in aqueous solution?

Answer 2

Base

Question 3

Any molecule that donates an electron pair in aqueous solution?

Answer 3

Lewis Base

Question 4

Any molecule that accepts an electron pair in aqueous solution?

Answer 4

Lewis Acid

Question 5

In a polyprotic strong acid, how do the H+ dissociate?

Answer 5

They dissociate together

Question 6

What is normality?

Answer 6

A normal is one gram equivalent of a solute per liter of solution.
Ex: hydrochloric acid is a strong acid that dissociates completely in water, a 1 N solution of HCl would also be 1 N for H+ or Cl- ions for acid-base reactions.

Question 7

How would you calculate the normality of a polyprotic strong acid?

Answer 7

([H+]/liter of solution) x however many protons dissociate

Question 8

5 mM can also be written how?

Answer 8

(5 x10^-3M)

Question 9

How would you calculate the pH of a diprotic strong acid, such as H2SO4?

Answer 9

multiply the concentration of the H2SO4 solution by 2 (because 2 protons are dissociating) to get [H+], then use pH= -log[H+]

Question 10

If the concentration of H+ was 1 x 10^-2, what would the pH be?

Answer 10

pH = -log(1 x 10^-2) = 2

Question 11

What is the formula used to calculate pH?

Answer 11

pH = -log[H+] or pOH = -log[OH-]

Question 12

What is the formula used to calculate the ion product of water?

Answer 12

[H+][OH-] = 10^-14 so [H+] = [OH-] = 10^-7

*true for all aqueous solutions

Question 13

A reaction that goes to equilibrium is called what?

Answer 13

reversible reaction

ex: ionization of water

Question 14

How do you calculated the equilibrium constant?

Answer 14

Keq = [products]/[reactants] = [C][D]/[A][B]

Question 15

Molecules that partially dissociate and individual protons dissociate at a different time and to a different extent?

Answer 15

weak polyprotic acids

Question 16

When an acid donates a proton, what does it become?

Answer 16

conjugate base [A-]

Question 17

When a base accepts a proton, what does it become?

Answer 17

conjugate acid [B+]

Question 18

A reaction containing an acid that dissociates can be defined as what?

Answer 18

acid-conjugate base pair

Question 19

To measure the amount of dissociation of an acid what steps would you take?

Answer 19

-define equilibrium constant
Keq = [H+][A-]/[HA] = Ka
-use pKa to determine [A-]
pKa = -log[A-] so Ka = 10^-pKa = [H+][A-]/[HA] 
*energy is neither created or destroyed, so [H+]=[A-]
so (10^-pKa)[HA]=[H+]^2
-then use [H+] to calculate pH
pH = -log[H+]`

Question 20

Process by which an acid is converted to a conjugate base in a step-wise procedure by addition of known concentration of titrant?

Answer 20

titration

Question 21

What is the half equivalence point?

Answer 21

moles of analyte = moles of conjugate acid/base
-point when half of the analyte has dissociated and so for an acid titration, [H+] = [HA]. The concentration of titrant added at half equivalence point is only half the concentration of analyte originally present. Therefore, at half-equivalence; pH = pKa.

Question 22

What is the equivalence point in a titration?

Answer 22

moles of titrant = moles of analyte.
-point at which the concentration of analyte (could be acid or base) is equal to the concentration of titrant because the analyte has completely dissociated

Question 23

What is the midpoint in a titration?

Answer 23

Same as half equivalence point

Question 24

What is the isoelectric point in a titration?

Answer 24

-point at which the polyprotic acid has dissociated and now has no net electrical charge

Question 25

How do you calculate the isoelectric point, pI, for a polyprotic acid

Answer 25

take the average of the 2 or more dominating pKa’s (for acids, only calculate the acids pKa’s

Question 26

What is the significance of the isoelectric point?

Answer 26

it is the point at which a polyprotic acid is least soluable in blood and electrolytes in the blood will associate with the acid and precipitate

Question 27

Weak acid-conjugate base pairs that resist changes in pH when small amounts of acid or base are added to solution are called what?

Answer 27

buffers

Question 28

What are buffers?

Answer 28

Weak acid-conjugate base pairs that resist changes in pH when small amounts of acid or base are added to solution

Question 29

Molecules with pKa’s in what range make good physiologic buffers?

Answer 29

6-8 such as histidine

Question 30

Henderson-Hasslebach

Answer 30

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