Acid Base Equill

Question 1

What is an Arrhenius acid

Answer 1

It is a substance that dissolves in water to release H+ ions

Question 2

What is an Arrhenius base

Answer 2

It is a substance that dissolves in water to release OH- ions

Question 3

By the Arrhenius Theory, acid-base reactions can only take place in what medium

Answer 3

Aqueous medium (water as solvent)

Question 4

What is a Bronsted acid

Answer 4

A Bronsted acid is a proton, H+, donator

Question 5

What is a Bronsted base

Answer 5

A Bronsted base is a proton, H+, acceptor

Question 6

What are amphoteric solvents

Answer 6

An amphoteric solvent can both donate and accept protons durinfg different conditions

They can act as both Bronsted acids and bases.

E.g: water

Question 7

During a reversible reaction that is also an acid-base reaction, what is the reactant-product pair called

Answer 7

A conjugate acid-base pair

Question 8

How do the members of the conjugate acid-base pair differ

Answer 8

They differ from each other in terms of a H+

Question 9

What is a lewis acid

Answer 9

A lewis acid is an electron-pair acceptor

Question 10

What is a lewis base

Answer 10

A lewis base is an electron-pair donator

Question 11

Are the Arrhenius acids a subset of Lewis acids

Answer 11

Yes

Question 12

Are the Arrhenius acids a subset of Bronsted acids

Answer 12

Yes

Question 13

Are Bronsted acids a subset of Lewis acids

Answer 13

Yes

Question 14

What is the strength of an acid dependant on

Answer 14

The extent of dissociation in an aqueous medium

Question 15

What is a strong acid and a weak acid

Answer 15

(i) A strong acid is an acid that will completely dissociate in aqueous medium
(ii) A weak acid is an acid that will not completely dissociate in aqueous medium

Question 16

What is the significance of a reversible acid-base reaction

Answer 16

The acid is a weak acid or the base is a weak base.

Question 17

What is a strong base and what is a weak base

Answer 17

(i) A strong base will completely ionise in aqueous medium

(ii) A weak base will partially ionise in aqueous medium

Question 18

What is an indicator of strength of acid

Answer 18

Extent of dissociation A (alpha) which is derived from [H3O+]equil./[Acid]ini

Question 19

Why is the extent of dissociation not a very accurate measurement of strength

Answer 19

It increases with decreasing concentration

Question 20

Why is concentration not a good indicator of strength of an acid

Answer 20

Concentration is not equivalent to extent of dissociation.

(i) concentration refers to the amount of acid dissolved in an aqueous medium
(ii) extent of dissociation refers to the ratio between concentration of acid dissociated to concentration of acid initially

Question 21

What is the Kc expression of the auto-ionisation of water

Answer 21

Kc=[H3O+][OH-]/[H2O]^2

Question 22

What is the significance of the Kw value

Answer 22

(i) At a temperature of 25°C, the product of [H3O+] and [OH-] will always be this value
(ii) For reactions involving the dissociating of acids and ionisation of bases, a change in [H3O+] will induce an inversely proportional change in [OH-] and vice versa

Question 23

What is the pH solution of an alkalinic solution

Answer 23

pH>7, where [OH-] is greater than 10^-7

Question 24

What is the pH level of an acidic solution

Answer 24

pH<7, [H3O+]>10^-7

Question 25

Logarithmic relationship between concentrations of [H3O+] and [OH-]

Answer 25

-14=log[OH] + log[H3O+]

Question 26

Given that auto-ionisation of water is endothermic, what is the relationship between the pH of water and temperature

Answer 26

Thought process Suppose there is an increase in temperature, (i) By Le Chatelier's principle, the endothermic reaction would be favoured (ii) [H3O+], [OH-] falls (iii) pH= -log[H3O+], thus pH falls

Question 27

Thought process regarding calculations of pH of strong acids and bases

Answer 27

(i) Find concentration of strong acid or bases (ii) Concentration of [H3O+] or [OH-] dependant on basicity (iii) Using pH formula, find pH

Question 28

Thought process for calculation of pH of weak acid or weak base

Answer 28

(i) Using formula [H3O+]=(Ka×c)^0.5, find [H3O+], if base replace products and replace Ka with Kb (ii) Use pH formula

Question 29

What is the