Acid and base

Question 1

Bronsted-Lowry definition of an acid and base?

Answer 1

an acid is a proton donor and a base is a proton acceptor

Question 2

the difference between a weak acid and a strong acid/base

Answer 2

A strong acid/base is completely dissociated in aqueous solution. Equilibrium constant large. Virtually no undissociated HA exists in aqueous solution.
A weak acid/base is partially dissociated in aqueous solution. Equilibrium constant very low.
At any one time, only 1% of HA molecules have converted to ions

Question 3

list of strong acids (pH1-2)

Answer 3

sulphuric acid (H2SO4)
nitric acid (HNO3)
hydrochloric acid (HCl)
HA + H2O -> H3O+ A-

Question 4

list of weak acids (pH 5-6)

Answer 4

acetic acid (CH3COOH)
carbonic acid (H2CO3)
HA + H2O <-> H+ +A-

Question 5

list of strong bases (pH 13-14)

Answer 5

sodium hydroxide (NaOH)
potassium hydroxide (KOH)
BOH + H2O -> B+ + OH- + H2O

Question 6

list of weak bases (pH 11-12)

Answer 6

ammonia (NH3)

B <-> BH+ + OH-

Question 7

water function as both acids and bases

Answer 7

A substance which can act as either an acid or a base is described as being amphoteric or autoprotic

H3O+: when water accepts a proton, and is acting as a base
OH-: when water donates(loses) a proton, and is acting as an acid

Question 8

Kw=[H3O+ + OH-]
Kw=[H+ + OH-]
and Why isn’t water isn’t written on the bottom of these equilibrium constant expressions?

Answer 8

This is OK provided you remember that H+(aq) actually refers to a hydroxonium ion. Both Kw expressions mean exactly the same thing

So little of the water is ionised at any one time, that its concentration remains virtually unchanged - a constant, hence it is omitted

At 25 °C, Kw is 1.0×10−14

Question 9

What is a pH indicator ?/ What are the properties of a good indicator?

Answer 9

A compound that changes color in solution over a narrow range of pH values
A good indicator changes the color suddenly and color change is distinct

Question 10

Equivalence point?

Answer 10

at which chemically equivalent quantities acid and base have been mixed

Question 11

end point?

Answer 11

When indicator changes color in solution

Question 12

conjugate pair

Answer 12

acid - base conjugate pair differs by just one proton.