Acids And Bases

Question 1

Why is pure water neutral ?

Answer 1

Conc of H+ ions = Conc of OH- ions

Question 2

Definition of Bronsted- lowery acid

Answer 2

Proton donor

Question 3

Bronsted-lowery base

Answer 3

Proton acceptor

Question 4

Equation for pH

Answer 4

pH= -log[H+]

Question 5

Equation for [H+] using pH

Answer 5

[H+]= 10^-pH

Question 6

Equation for Kw

Answer 6

Kw= [H+][OH-]

Question 7

Kw of pure water

Answer 7

Kw= [H+]^2

Question 8

Effect of temperature increase on pH and neutrality of water

Answer 8

Increase in temp= equilibrium shifts right to lower temp

More [H+] and [OH-]

Kw and pH increase

Still neutral

Question 9

Calculating pH of strong bases

Answer 9

Conc of OH- equal to conc of solution

[H+] = Kw / [OH-]

pH= -log[H+]

Question 10

Reactions between strong acids and strong bases

Answer 10

Mol of H+ = conc x vol
Mol of OH- = conc x vol

Mol excess = H+ mol - OH- mol or visa versa

Conc excess = mol excess / total new volume

pH= -log[H+] or [H+] = Kw / [OH-]

Question 11

General chemical equation of strong acid

Answer 11

HX = H+ + X-

Question 12

Strong acids to know

Answer 12

HCl
HNO3
H2SO4

Question 13

Weak acids to know

Answer 13

Carboxylic acids

Question 14

Strong bases to know

Answer 14

NaOH
KOH
Ba(OH)2

Question 15

Weak bases to know

Answer 15

Ammonia

Question 16

Equation for Ka (acid dissociation constant)

Answer 16

Ka= [H+][A-] / [HA]

Question 17

Equation for pKa

Answer 17

pKa = -log(Ka)

Question 18

Ka of weak acids in aqueous solution with nothing else added

Answer 18

Ka = [H+]^2 / [HA]

Question 19

calculating the volume of an acid

Answer 19

calculate [H+] from pH
calculate moles of HCl (mol x conc)
vol = mole HCl / [H+]

Question 20

what does the phrase “fully dissociates” tell you about the nature of an acid

Answer 20

it is a strong acid

Question 21

calculating the pH of a diluted acid

Answer 21

Calculate [H+] = (initial vol/ total new vol) x conc

pH = -log[H+]

Question 22

general value of Kw

Answer 22

1.00 x 10-14 mol^2 dm^-6

Question 23

explain why chloroethanoic is a stronger acid than ethanoic acid

Answer 23

chlorine is electronegative and so withdraws electrons, making OH bond more polar thus H+ is more easily lost

Question 24

explain why data books so not usually contain values of Ka for strong acids

Answer 24

Ka value for a strong acid is very high/ infinite

Question 25

why would the pH of magnesium hydroxide be lower than that of calcium hydroxide

Answer 25

it is less soluble