11: Acids And Bases

Question 1

what is autoionization

Answer 1

a spontaneous dissociation of water by which Small amounts of H+(aq) and OH−(aq) are formed.
- it is reversible

Question 2

What is the only way to change the value of the Equilibrium constant K

Answer 2

the only way to change the value of the equilibrium constant is by changing the temp.
- changing the conc. of the reactants has no effect on it

Question 3

Lewis, BronstedLowry ,Arrhenius definition of Acid and Base

Answer 3

Lewis: Acids are electron pair acceptors in solution. Bases are electron pair donors in solution
Bronsted: Acids are proton donors; bases are proton acceptors
Arrhenius:Acids produce H+ in aqueous solution. Bases produce OH− inaqueous solution.

Question 4

What are strong acids and bases

Answer 4

Acids and bases that dissociate completely and stay dissociated.
Strong means: completely dissociating.
dissociation is considered 100 percent, which makes it easier to calculate pH

Question 5

Strong acid and strong bases examples

Answer 5

Strong acids
- hydrochloric acid
- Hydrogen Iodide (hydroiodic acid)
- Hydrogen Bromide  (hydrobromic acid)
- Nitric acid
- sulphuric acid
- Hydrogen chlorate ( perchloric acid)
Strong bases
-  all Group I hydroxides, Ba(OH)2 and Sr(OH)2

Question 6

What is the pH of 1.0M of any strong acid

What is the pH of 1.0M of any strong base

Answer 6

Acid: it is always zero
Base: it is 14

Question 7

What are Weak acids or bases

Answer 7

Acids and bases that partially, reversibly dissociate are referred to as weak acids or bases
Weak means: i partial or reversible dissociation

Question 8

What is A conjugate pair

Answer 8

refers to two molecules that have identical

molecular formulas except that one of them has an additional H+.

Question 9

What are buffers

Answer 9

are solutions used to minimize (not prevent) a change in pH when an additional acid or base is introduced into solution

Question 10

Some properties of the Henderson-Hasselbalch equation

Answer 10

-If you’re given the number of moles of HA and A− in the test question, don’t waste time converting to molarity just to plug into the HendersonHasselbalch equation; just use moles.
- If the number of moles of HA and A− are equal, then the HendersonHasselbalch equation can be simplified to pH = pKa (or pOH = pKb).
-The pH of a buffer solution doesn’t change with changing volume, since volume does not appear in the equation. Therefore, diluting or concentrating (through evaporation or osmosis) a buffer will not change its
pH. ONLY he number of moles matters, bcs both the salt and the acid have the same volume, they cancel each other out.

Question 11

The most important property of a buffer.

Answer 11

Diluting or concentrating a buffered solution does not change its pH

Question 12

an acid-base titration

can be used to figure out the following:

Answer 12

1. concentration of an acid or base
2. whether an unknown acid or base is strong or weak
3. pKa of an unknown acid or pKb of unknown base

Question 13

What is the equivalent point, or inflection point, or end point.

Answer 13

This is the point during the titration where just enough titrant (in moles) has been added to completely neutralize the subject acid or base

Question 14

Why can’t we find out the pKa or pKb of a strong acid or base

Answer 14

B/c they react completely

Question 15

What happens at half-equivalence point

Answer 15

There is equal amounts of the unknown acid or base and it’s conjugate. So, the Henderson-Hasselbalch equation applies, the sol is a buffer.

Question 16

For titration of weak acid with strong base pKa is?

For titration of weak base with strong acid pKb is

Answer 16

1: pH (at half equi point) = pKa
2: pOH (at half equi point) = pKb
Therefore the pH is for the weak acid

Question 17

What is an indicator and it’s pH range

Answer 17

Is a conjugate pair of a weak acid or base, where each conjugate is a different color.
- the acid base indicator changes color in a pH range +or- 1 of its pKa
Ex: thymol blue, pKa= 2
Undergoes a red to blue color change in the pH range 1 to 3.

Question 18

What is the dissociation percentage of weak acids and bases

Answer 18

Weak acids dissociate less than 10% in solution. Thus, in a solution of HF, over 90% of the HF molecules stay combined.
- it is also the same for weak bases

Question 19

What are polyprotic and monoprotic acids

Answer 19

-Polyprotic acids are acids that donate more than 1 proton.
Ex: phosphoric acid
N.B: each dissociation is weaker than the one before

Monoprotic acids are ones that can only donate 1 proton

Question 20

Different btn pKa of a strong acid and a weak acid

Answer 20

• the stronger the acid, the lower its pKa value is

It is like pH

Question 21

The conjugate bases of strong acids (rem the list)

Answer 21

All six of ions of strong acids do not act as conjugate bases (they are neutral, rem the rules)