2.Acids and ph

Question 1

What is a salt?

Answer 1

salts are ionic compounds formed when the H+ ions in acids are replaced by metal IONS or ammonia ions.

Question 2

What is a base

Answer 2

a proton acceptor

Question 3

What is an acid

Answer 3

a proton donor (releases H= ions in aqueous solution)

Question 4

what is a alkali

Answer 4

Releases OH- ions when in a water solution

Question 5

whys are things classified as a base but not as an alkali?

Answer 5

IF it accepts protons but dosnt dissolve it cant be and alkali because an alkali need to be able to release OH- ions into a solution which cant happen if its insoluble.

Question 6

Acid + metal oxide —->

Answer 6

Salt + water

Question 7

Acid + metal (reactive) —->

Answer 7

salt + hydrogen gas

Question 8

Acid + metal carbonate—->

Answer 8

salt + CO2 + water

Question 9

Acid + metal hydro carbonate —->

Answer 9

salt + water + CO2

Question 10

Acid + alkali —->

Answer 10

salt + water

Question 11

3 types of bases

Answer 11

Metal hydroxides - HO- ion reacts with H+ to from waterMetal Oxides- Ammonia (and organic amino componds)

Question 12

dilute amodia decolourises which halid ions?

Answer 12

Chloride

Question 13

conc ammonia decoulourises which halide ions?

Answer 13

Bromide, and Chloride

Question 14

insoluble compoud + acid is slow becuase ….

Answer 14

only the surface of the compound can react at once.

Question 15

methyl orange colours

Answer 15

Alkaline-yellowneural(bit more acidic 4ph) -orangeacidic - red

Question 16

Phenolphthalein colours

Answer 16

acid - colorlessalkali-pink

Question 17

what is a strong acid?

Answer 17

Completly disassociates in aqeuous solution

Question 18

what is a weak acid

Answer 18

partially disasociates in aqeuous solution

Question 19

what must be present for a something to act as an acid?

Answer 19

a base, as a H⁺ ion cannot exist on its own

Question 20

what is a conjugate base?

Answer 20

a species formed when a proton is removed from an acid

(has the possibility to revert back to acid by accepting a proton)

Question 21

what is a conjugate acid?

Answer 21

a species formed when a proton is added to a base

(has the possibility to revert back to a base by losing a proton)

Question 22

acid-base pair

Answer 22

a pair of two species that transform into each other by the loss/gain of a proton

can be labled 1.acid,1conjugate base etc

Question 23

ph=

Answer 23

-log[H⁺]

Question 24

[H⁺]=

Answer 24

10^-ph

Question 25

strong alkali

Answer 25

1 OH^- per alkali molecule

Question 26

K_w=

Answer 26

ionic product of water

[H⁺][OH^-] = 1x10^-14

Question 27

effect temperature has on water’s ph and K_w

Answer 27

H₂O <=> H⁺+OH^- is endothermic

inc temp = shift right = K_w increase = lower Ph

however the solution is still neautral as [H⁺]=[OH^-]

Question 28

K_a =

Answer 28

acid disociation constant for weak acids

[H⁺][A^-]/[HA]

=10^-Pk_a

Question 29

pK_a =

Answer 29

-log K_a

Question 30

what does H₃O⁺ represent

Answer 30

hydronium ion or H⁺ in aq sol

Question 31

what values of pka and ka for a strong acid?

Answer 31

small pH_a and a high K_a

Question 32

approximation made in calculating weak acid ph

Answer 32

equ [HA] = initi [HA] as very little disasociates

([HA]-x=[HA]

Question 33

sig figs for ph

Answer 33

2.21 is 2 sig figures which is the best numebr to give them to

Question 34

setup for ph calcs

Answer 34

HA <=> H⁺ + A^-

Initial: [HA] 0 0 .

Initial: [HA] (-x) x x .

ingnor -x

0 is replaced witht he conc in buffes

Question 35

What is a buffer solution

Answer 35

a solution which resists(minimises) changes in ph , upon an addition of small amounts of acid or alkali

a mixture of a weak acid and its conjugate base

Question 36

2 ways to make a buffer solution

Answer 36

1. Add a weak acid and a salt of the weak acid(conjugate base)
2. Add excess weak acid to an aqueous alkali.

Question 37

how to lay out buffer solution questions

Answer 37

• Equilibrium equation
• Effect upon adition of H⁺ , what it reacts with where the equ shifts to
• Effect upon adition of OH^- , what it reacts with where the equ shifts to

Question 38

an example of a buffer in nature?

Answer 38

blood

H₂CO₃<=>H⁺ + HCO₃^-

Question 39

what is the equivelance point

Answer 39

the point in a titration at which the volume of one solution has reacted exactly with the volume of the second solution.

Question 40

what is the endpoint?

Answer 40

the point in a titration at which there are equal concs of the weak acid and conj base forms of an indicator.

Question 41

what is an indicator

Answer 41

usually a weak acid , with two different colours for its acid and conj base.

Question 42

indicator equation

Answer 42

HIn <=> H⁺ + In^-

Question 43

indicator for weak acid/strong base?

Answer 43

phenolphthalein

Question 44

indicator for weakbase/strong acid

Answer 44

methyl orange

Question 45

how is an indicator chosen?

Answer 45

the ph value of the end point is as close to the equivelance point as possible. (or on nthe vertical section) so that one drop will change its colour

Question 46

indicator for weak acid / weak base

Answer 46

none as there is no vertical section so colour change is too gradual

Question 47

titration curves

Answer 47

Question 48

what is enthalpy change of neutralisation?

Answer 48

the energy change that accompanies the neutralisation of an aqeuous acid by an aqeuous base to form one mole of water under standard conditions

Question 49

weak vs strong acid enthalphy of nutralisation

Answer 49

weak acid have less exothermic enthalphys oif neutralisation as some energy is used in breaking hydrogen bongs (in things like carboxillic acids)