Acids and Bases

Question 1

What is Ka? What does it tell us?

Answer 1

Acid dissociation constant. It tells us the tendency of the acid to dissociate in water, with stronger acids having a higher Ka value

Question 2

How does a change in the hydrogen/hydronium concentration translate to a pH change?

Answer 2

A tenfold increase in the hydrogen concentration is a decrease in pH by 1 unit. And vice versa

Question 3

For oxalic acid, what is the compound called when it loses one proton, and what is it called when it loses the second proton?

Answer 3

Monosodium oxalate after losing the first one, disodium oxalate after losing the second one

Question 4

What 3 things can a titration tell us?

Answer 4

1. How many protons a molecule can lose
2. What is the pKa for each proton
3. What is the concentration of the acid in solution

Question 5

What is a titration?

Answer 5

When a strong base (we know the concentration) is added in small increments to an unknown concentration of weak acid

Question 6

What is on the x-axis and y-axis of a titration curve?

Answer 6

x-axis has the molar equivalents of strong base. y-axis has the pH

Question 7

How much strong base needs to be added so that the pH = the pKa of the acid?

Answer 7

1/2 of a molar equivalent

Question 8

How much strong base needs to be added so that the solution reaches the equivalence point?

Answer 8

1 molar equivalent

Question 9

What happens when 0.5 molar equivalents, 1 molar equivalents, 1.5 molar equivalents, and 2 molar equivalents of strong base are added in the titration of a diprotic acid?

Answer 9

0. 5: pH = pKa1
   1: equivalence point 1
1. 5: pH = pKa2
   2: equivalence point 2

Question 10

What is the protonation state of both protons in a diprotic acid when before 0.5, 0.5, 1, 1.5, and 2 molar equivalents of strong base are added?

Answer 10

Before 0.5: both in HA form

0. 5: More acidic proton is 50% HA and 50% A-, less acidic proton is in HA form
   1: More acidic proton is in A- form, less acidic in HA form
1. 5: more acidic proton is in A- form, 50% of less proton is in HA form and 50% in A- form
   2: Both in A- form

Question 11

What is a buffer solution made of?

Answer 11

An aqueous solution of a weak acid and its conjugate base

Question 12

Why are buffers in living systems super important?

Answer 12

They resist drastic changes in pH when small amounts of acid or base are added, and pH will affect protein shape and function

Question 13

What is the buffering range?

Answer 13

One pH unit above and below the pKa

Question 14

When is a buffer most effective?

Answer 14

When [HA] = [A-]

Question 15

What buffer is used in the cytoplasm of cells?

Answer 15

Phosphate buffer, with a pKa of 7.2

Question 16

What buffer is used in blood?

Answer 16

CO2 and hydrogen carbonate, keeps blood at about 7.4

Question 17

What is respiratory alkalosis?

Answer 17

Excessive breathing causes a loss of CO2 and the pH of the blood to increase

Question 18

What is acidosis?

Answer 18

When the brain breaks down fatty acids for energy and releases weakly acidic ketone bodies that causes a drop in the pH of blood

Question 19

How can pH change the water solubility of a molecule?

Answer 19

Organic compounds are most soluble when charged, and less soluble when protonated