(BLUE) pH And Ka

Question 1

What is the definition of an acid and alkali/base

Answer 1

Acid : is a proton donor / accepts a lone pair of electrons

Base/alkali : is a proton acceptor / donates a lone pair of electrons

Question 2

What is a conjugate acid-base pair

Answer 2

It is the base that is formed from an acid in a reaction e.g NH4+ to NH3 , strong acids produce weak bases and vise versa

Question 3

What does amphoteric mean

Answer 3

Can act as both an acid and a base

Question 4

What is the definition of a strong acid

Answer 4

A strong acid is an acid which fully dissociates (ionises) when it is dissolved in water
Strong acids have weak conjugate bases

Question 5

What is the definition of a weak acids

Answer 5

Is an acid which only partially dissociates (ionises) when it dissolves in water
Weak acids have strong conjugate bases

Water is a weak acid it’s conjugate pair hydroxide is a very strong base

Question 6

What colour methyl orange in
Acid and base

Answer 6

Acid : red
Base : yellow

Question 7

What colour phenolphthalein in
Acid and base

Answer 7

Acid: colourless
Base:: bright pink

Question 8

What colour bromothymol blue in
Acid and base

Answer 8

Acid : yellow
Base : blue

Question 9

What colour bromophenol blue
Acid and base

Answer 9

Acid : yellow
Base : purple

Question 10

What is the definition of pH

Answer 10

pH = -log(base: 10)(H+)

Question 11

How do you go from pH to conc of H+

Answer 11

[H+] = 10^-pH

Question 12

What is the constant for Kw

Answer 12

1x10^-14

Question 13

What is the equation for Kw

Answer 13

Kw= [H+][OH-]

Question 14

What is the equation for Kc

Answer 14

Kc= product conc / reagent conc

Question 15

What does p mean

Answer 15

-log

Question 16

What is the equation of Ka

Answer 16

Ka= Acid dissociated conc x H conc / acid conc

Question 17

What is the definition of enthalpy of neutralisation

Answer 17

The energy released when one mole of water is produced from an acid-base reaction at standard room temperature and pressure

Question 18

Why do HCL and HNO3 have similar enthalpy of nutralisation

Answer 18

Because both HCL and HNO3 are monoprotic therefore releasing 1H+ , both strong acids therefore fully dissociate

Question 19

Why does CH3COOH have a lower enthalpy of neutralisation than HCL

Answer 19

Ethanoic acid is a weak acid which means it does not fully dissociate
Also energy is used to break O-H bond which is Endothermic

Question 20

Explain the increasing acidity of ethanoic acid —>benzoic acid —-> methanoic acid

Answer 20

CH3 donates e- density , which strengthens the O-H bond more, which makes it easier to loose the hydrogen

Question 21

Explain the increasing acidity of chloroethanoic acid —-> tricholoroethanoic acid

Answer 21

Cl is very electronegative which pulls the e- density away from the O-H bond , weakening it

Question 22

Page 16
Why does phenylamine have the lowest pH (weakest base)

Answer 22

Lone pair of e- on N delocalised into the pie system so not available to accept H+

Question 23

Page 16
Why does dimethylamine have the highest pH

Answer 23

CH3 donates electron density therefore Lone pair of electrons on N more available to accept H+