Acids and Bases (Physical)

Question 1

Define Bronsted-Lowry acid
Define Bronsted-Lowry base
Define the reaction between the two.

Answer 1

• acid: proton donor
• base: proton acceptor
• reaction: reaction involving the transfer of a proton.

Question 2

Define:
- Monoprotic acid
- Diprotic acid
- Triprotic acid

Answer 2

• mono- acid that releases one H+ ion per molecule.
• do- acid that releases two H+ ions per molecule.
• tri- acid that releases three H+ ions per molecule.

Question 3

Give the definition of pH.

Answer 3

-log[H+]

(2d.p)

Question 4

Equation to find the concentration of H+ ions in a solution once another solution is added.

Answer 4

[H+] in original solution x (old volume / new total volume)

Question 5

Describe where Kw comes from.
What is the usual value for Kw at 298K?

Answer 5

Kw = Kc x [H2O]

• During; H2O —(reversible symbol)-> OH- + H+ reaction there is so much water that [H2O] is seen as a constant value, while [H+] and [H2O] are variables.
• As; Kc = ( [H+] x [OH-] ) / [H2O], therefore; Kc x [H2O] = [H+] x [OH-] and Kw = Kc x [H2O]
• This means; Kw = [H+] x [OH-]

Kw = 1 x 10^-14 mol^2dm^-6

Question 6

What is the effect of temperature on the pH and neutrality of water in terms of Kw?

Answer 6

H2O —(reversible symbol)-> OH- + H+ (—> exothermic)

• As temperature increases, equilibrium shifts right to endothermic direction to oppose increase.
• Therefore [H+] and [OH-] increase, Kw increases and pH decreases.
• However water still neutral as [H+] = [OH-]

Question 7

Give the definition of neutral

Answer 7

[H+] = [OH-]