21.1 buffer solutions

Question 1

define a buffer solution

Answer 1

a system that minimises pH changes when small amounts of an acid or a base are added

Question 2

what makes up a buffer solution?

Answer 2

2 components
weak acid
conjugate base

Question 3

what do the 2 components that make up a buffer solution do?

Answer 3

weak acid- removes added alkali
conjugate base- removes added acid

Question 4

what happens when alkalis or acids are added to a buffer?

Answer 4

2 components in the buffer solution react and are used up

Question 5

what happens when one component in the buffer has all reacted?

Answer 5

solution loses its buffering ability towards added acid/alkali

Question 6

what makes up a weak acid buffer solution?

Answer 6

a weak acid and it’s conjugate base

Question 7

what are the two ways buffer solutions can be made?

Answer 7

weak acid buffer solution
partial neutralisation of the weak acid

Question 8

how does partial neutralisation of a weak acid work?

Answer 8

weak acid is partially neutralised by the strong alkali forming the conjugate base
some of the weak acid doesn’t react
resulting solution contains a mixture of the salt of the weak acid and any unreacted weak acid

Question 9

what controls the pH in an acid buffer solution?

Answer 9

conjugate acid-base pair

Question 10

what happens when you add a small amount of acid to the buffer solution?

Answer 10

the concentration of H+ increases which causes the H+ to react with the conjugate base
equilibrium position shifts to the left which removes most of the H+ ions

Question 11

what happens when you add a small amount of alkali to the buffer solution?

Answer 11

concentration of OH- ions increases and they react with the H+ ions to form water
HA dissociates which shifts the equilibrium position to the right to restore most of the H+ ions

Question 12

when concentration of HA= concentration of A-…

Answer 12

pH of the buffer solution is the same as the pKa value of HA

Question 13

how do you calculate concentration of H+ for a buffer solution?

Answer 13

Ka x [HA]/[A-]