Acids And Bases

Question 1

What are alkalis

Answer 1

They are based that are soluble in water

Question 2

What do group 1 metals releases when they react with water

Answer 2

Hydroxides

Question 3

What are the problems with the arhenius model

Answer 3

• he only described them in terms of H+ and OH- ions
• he only describe acids and bases that are in solution

Question 4

What happens to Kw when temperature increases

Answer 4

• temperature increases Kw increases because the the ionisation of water is endothermic so the conc of H+ and OH- increases

Question 5

When is a solution neutral

Answer 5

[H+] = [OH-]

Question 6

What does a change in concentration to [H+] or [OH-] do and why

Answer 6

It doesn’t affect equilibrium because an increase in the concentration of one leads to the decrease in the concentration of the other leading to Kw being the same

Question 7

Describe a titration.

Answer 7

• rinse pippette with acid/alkali, then fill with pipette filler
• place 25cm3 of acid/alkali of known concentration in conical flask
• add few drops of suitable indicator
• rinse burette with acid/alkali, then fill it
• record start volume
• add small portions of acid/alkali from burette
• stir solution in conical flask
• add acid/alkali dropwise as you approach end point
• stop adding acid/alkali when colour change occurs
• record end volume
• repeat until 2 concordant results (within 0.10cm3 of each other) are obtained
• calculate mean titre value

Question 8

How do buffers work?

Answer 8

Equilibrium reaction removes added H+ and OH- ions

Question 9

How do you improve accuracy with a pH meter?

Answer 9

• callibrate first using buffer solution of known pH

Question 10

Why is the equivalence point not always neutral?

Answer 10

salt produced may be basic/acidic

Question 11

Acid + metal oxide

Answer 11

Salt + water

Question 12

Acid + metal carbonate

Answer 12

Carbon dioxide + water

Question 13

Acid + metal

Answer 13

Salt + hydrogen

Question 14

For a strong acid + strong base where would the equivalence point be

Answer 14

= 7

Question 15

For a strong acid + weak base where would the equivalence point be

Answer 15

< 7

Question 16

For a weak base and strong acid where would the equivalence point be

Answer 16

> 7

Question 17

For a weak acid + weak base where would the equivalence point be

Answer 17

= 7

Question 18

For a weak base + strong acid where would the equivalence point be

Answer 18

< 7

Question 19

For a strong base + weak acid where would the equivalence point be

Answer 19

> 7

Question 20

Why does adding water to a buffer not affect pH

Answer 20

Because diluting a buffer affects [HA] and [A-] equally