Acids and Bases (P1)

Question 1

How do you calculate pH from H+ concentration?

Answer 1

-log10(H+ concentration)

Question 2

How do you calculate H+ concentration from pH?

Answer 2

10^-pH

Question 3

Define a Bronsted-Lowry acid

Answer 3

A H+ donator

Question 4

Define a Bronsted-Lowry base

Answer 4

A H+ acceptor

Question 5

Give an example of water acting as a base

Answer 5

HCL +H2O —> H3O+ + Cl-

Question 6

Give an example of water acting as an acid

Answer 6

H2O + NH3 —> OH- + NH4+

Question 7

What is H3O+ called?

Answer 7

An oxonium ion

Question 8

Define a strong acid/base

Answer 8

An acid/base that completely dissociates into ions in an aqueous solution

Question 9

Give an example of a) two strong acids and b) a weak acid

Answer 9

a) Sulfuric acid or hydrochloric acid

b) Ethanoic acid

Question 10

Give an example of a) two strong bases and b) a weak base

Answer 10

a) Potassium hydroxide and sodium hydroxide

b) Ammonia

Question 11

Where does equilibrium shift to when Ka increases in value?

Answer 11

The right

Question 12

Why doesn’t the expression for Kw contain the concentration for water?

Answer 12

Water only dissociates slightly and it’s concentration is effectively constant.

Question 13

Why does the value of Kw increase with temperature?

Answer 13

As temperature increases, more water disscoiates into H+ and OH-
Dissociation is endothermic
So the equilibrium moves to the RHS to oppose the change of a temperature increase

Question 14

How do acids and bases act as buffers?

Answer 14

Acid: Increase in concentration of H+ ions, equilibrium moves to the left.
Alkali: OH- reacts with H+ ions, equilibrium moves to the right (to replace the H+
ions)
Concentration of H+ remains (almost) constant