Acids, bases and buffers

Question 1

Bronsted lowry acid

Answer 1

Proton donors, releasing H+ ions into a solution. Alwyas combine with h20 to form hydroxonium ions H30+

Question 2

Bronsted lowry base

Answer 2

Proton acceptors

Question 3

Alkali

Answer 3

A base that dissolved in water, releasing OH- ions

Question 4

Hydroxonium ions

Answer 4

H30+

Question 5

Monobasic acids

Answer 5

Give away one hydrogen

E.g. HCL

Question 6

Dibasic acids

Answer 6

Give away two hydrogens

E.g. H2SO4

Question 7

Tribasic acids

Answer 7

GIve away three hydrogens

E.g. H3PO4

Question 8

What are conjugate pairs

Answer 8

Species that are linked by the transfer of a proton
Always on opposite sides of teh equation
The speies that lost a proton = conjugate base and the species that gained a proton is the conjugate acid

Question 9

Outline the acid base theory and how its changed

Answer 9

Early ideas of acids being sour and alkalis from plant ahes
Base+ acid= solid form
Acids contain hydrogen that can be replaced by metal
ACids form H+ ions and bases form OH- ions
Acid base reactions tranfer protons, H+, An acid donates a proton and a base accepts a proton

Question 10

Metal+ acid

Answer 10

Salt adn hydrogen
The metal atoms donate electrons to teh H+ ions in the acid solution
Metal oxidised and ydrogen reduced

Question 11

Carbonates+ acid

Answer 11

Co2 and h20

Question 12

Metal oxides( most insoluble bases)+ acids

Answer 12

H20 and salt

Question 13

The pH scale- devised by who?

Answer 13

Soren Soreenson

Question 14

Strong acids

Answer 14

Completely dissociate

The conc of H+ ions is therefore the same as the conc of the acid

Question 15

Converting H+ conc to pH

Answer 15

• log

Question 16

Converting pH to H+ conc

Answer 16

shift log -

Question 17

pH of a diluted strong acid?

Answer 17

h+= H+ old * new vol/old vol

Question 18

if you have a diprotic acid and are finding conc of h+ from ph?

Answer 18

divide by 2

Question 19

WEak acids

Answer 19

Partially dissociate

Equilitbirum mixture

Question 20

What is used for weak acids adn finding equilibium

Answer 20

Ka= H+ * A_

/ HA - for diprotic, h+ squared

Question 21

THe larger the Ka value…

Answer 21

Th further the equilibrium is to the right and hte ggreater the dissociation and acid strength

Question 22

pKa

Answer 22

Making Ka into a whole number
-logka = pka
ka= shift log - pka

Question 23

Stronger acid=……. ka =……. pka

Answer 23

Larger ka value

Smaller pKa value

Question 24

What are teh 2 assumptions amde for calculating Ka

Answer 24

h+= A-
only small amounts of h+ from dissociation of water

Ha( equilibrium)= HA (start)
equ is smaller , but dissociation is small

Question 25

Ka simplified

Answer 25

H+= square root of | KA* HA

Question 26

finding the pH of a strong base?

Answer 26

Kw= H * OH

Question 27

What is the value of Kw at 25 degrees

Answer 27

1* 10 -14

Question 28

What is Kw called

Answer 28

IOnic product of water

Question 29

pH of a diluted base

Answer 29

OH-= oh old * old/new volume H+= kw/oh

Question 30

What can you use to remove added acid AND alkali

Answer 30

ethanoic acid CH3COOH--- H+ + CH3COO- ACt as 2 resevoirs that are a le o act inependently to remove aka and acd

Question 31

Buffer solutions

Answer 31

A system that minimises pH changes when small amounts of acid or base are added Contains 2 components to remove added acid or alkali

Question 32

WEak acid and conjugate base - role of buffers

Answer 32

The weak acid remoes added alkali | The conjugate base removes added acid

Question 33

WHat are the 2 ways you can prepare acid buffer solutions

Answer 33

Preparation from a weak acid and its salt Weak acid and a strong akali, partial neutralization

Question 34

Preparation from a weak acid and its salt - buffer

Answer 34

The salt fully dissociated and the weak acid only slightly dissoccaites e.g. ethanoic acid and sodium ethanoate

Question 35

Weak acid and a strong alkali - buffer making

Answer 35

NEUTRLISATION Add an aqueous solution of alklai, such as NaOH, to an excess of the weak acid The weak acid is partially neutralised by the alkali, forming the conjugate base. Some of the weak acid is left over unreacted. The resulting solution contains a mixture of a salt of the weak acid and any unreacted weak acid

Question 36

What does the buffer equilibrium solution contain

Answer 36

UNdissociated acid(HA) Lots of teh acids conjugate base( a-) Enough h+ ions to make the solution acidic

Question 37

What happens when acid is added to buffer solution

Answer 37

H+ increases H+ ions react with the conjugate base, A- The equilibrium shifts to the left, removing most of the H+ ions

Question 38

When alkali is added o buffer solution

Answer 38

OH- increases The small concentration of H+ ions reacts with the oh ions( =h20) HA dissociates shifting the equilibrium to the right to restore the H+ ions

Question 39

When are buffers most effectie

Answer 39

WHne there are equal concentrations of the weak acid and its conjugate base HA= A-

Question 40

teh pH of the buffer solution=

Answer 40

The pKa value of HA

Question 41

Calculating pH value of a buffer

Answer 41

The salt of the conjugate base is fully dissociated- equilibrium conc of A- is the same as intitial conc of the salt HA is only slightly dissociated, so assume that its equilibirum concentration is the same as its intial conc H+= ka* HA/a- ( weak acid conc/base conc) then -log

Question 42

What pH does the blood plasma need to be

Answer 42

between 7.35 and 7.45

Question 43

What happens if blood plasma falls below region it needs to be

Answer 43

Acidosis

Question 44

What happens if blood plasma GOES ABOVE region it needs to be

Answer 44

Alkaliosis

Question 45

What is the buffer called for blood

Answer 45

carbonic acid hydrogen carbonate | H2CO3

Question 46

Addition of H+- in the blood

Answer 46

H+ increases H+ ions react wiht conjugate base, HCo3- The equilbrium shifts to the left, removing most H+ ions H2co3--- H+ + Hco3

Question 47

On addition of OH- in the blood

Answer 47

OH- increases The small concs of H+ ions reacts with the OH- ions The h2Co3 dissociates, shifting the equilibirum position ot the RIGHT to restore most of the H+ ions