Inorganic and physical chemistry - part 2

Question 1

at equilibrium what is equal?

Answer 1

the rates of forward and reverse reaction

Question 2

what can the position of equilibrium be changed by?

Answer 2

• concentration
• temperature
• pressure

Question 3

what is the equilibrium constant represented by?

Answer 3

K

Question 4

if K=1, what does it show?

Answer 4

that the reaction is at equilibrium

Question 5

if K is large, what does it show?

Answer 5

that the products are favoured

Question 6

if K is small, what does it show?

Answer 6

that the reactants are favoured

Question 7

what effect does concentration have on the value of K?

Answer 7

no effect, value of K remains the same

Question 8

what is Le Chatelier’s principle?

Answer 8

when a reaction at equilibrium is subjected to change, the composition alters in such a way as to minimise the effects of the change

Question 9

does pressure have an effect on the value of K?

Answer 9

no

Question 10

if the temperature is decreased what happens to the value of K?

Answer 10

value of K decreases

Question 11

if the temperature is increased what happens to the value of K?

Answer 11

value of K increases

Question 12

what is the Bronsted-Lowry definition of an acid?

Answer 12

proton donor

Question 13

what is the Bronsted-Lowry definition of a base?

Answer 13

proton acceptor

Question 14

if an acid/base is described as being strong, what does this mean?

Answer 14

it is fully dissociated into ions

Question 15

what are some examples of a strong acid?

Answer 15

• hydrochloric acid
• nitric acid
• sulphuric acid

Question 16

if an acid/base is described as being weak, what does this mean?

Answer 16

it is incompletely dissociated into ions

Question 17

why is water described as being amphoteric?

Answer 17

it can behave as an acid or a base

Question 18

what is a monoprotic acid?

Answer 18

it donates only one proton per molecule

Question 19

as Ka increases, what happens to the strength of the acid?

Answer 19

strength of acid increases

Question 20

as pKa increases, what happens to the strength of the acid?

Answer 20

strength of acid decreases

Question 21

why are strong acids better conductors?

Answer 21

the acid is fully dissociated into ions

Question 22

will a strong acid need more, less or equal volume to neutralise compared to a weak acid?

Answer 22

equal volume of alkali needed to neutralise

Question 23

what is the pH of a salt of a strong acid + strong base

Answer 23

pH = 7

Question 24

explain why the pH decreases in a salt solution of a strong acid + weak base (ammonia example)

Answer 24

• concentration of OH ions in water decreases due to ammonia equilibrium
• water equilibrium shifts to the right
• more hydrogen ions produced

Question 25

explain why the pH increases in a salt solution of a weak acid + strong base (ethanoic acid example)

Answer 25

- concentration of H ions in water decreases due to ethanoic acid equilibrium - water equilibrium shifts to the right - more OH ions produced

Question 26

what is an indicator used for?

Answer 26

used to determine the end-point in an acid-alkali titration

Question 27

is a strong or weak acid usually used for an indicator?

Answer 27

weak acid

Question 28

at which point in the reaction should an indicator change colour?

Answer 28

in the pH range when the pH is changing very rapidly

Question 29

what happens to the pH of a buffer solution?

Answer 29

pH remains approximately constant when small amounts of acid or base are added or solution is diluted with water

Question 30

what does an acid buffer consist of?

Answer 30

a weak acid and one of its salts with a strong base

Question 31

what does a basic buffer consist of?

Answer 31

weak base and one of its salts