Acids and Bases

Question 1

pH = -log[H+]

Answer 1

[H+]=10^-pH

Question 2

Kw does NOT include [H20]

Answer 2

concentration is constant
in large excess
VERY high conc compared with [H+] and [OH−]

Question 3

Kw increases as temp increases

Answer 3

dissociation of water = ENDO

equilibrium moves to OPPOSE increase in temp

Question 4

weak

Answer 4

slightly dissociate

Question 5

calcium hydroxide?

Answer 5

Ca(OH)2 -> [OH-] x 2

Question 6

acid dissociation

Answer 6

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

OR [H+]^2 instead of [H+][A-] for acids only

Question 7

effect on pH of buffer solution

Answer 7

no change

H+ removed by A- forming HA

Question 8

how to decrease pH of aq sol of weak acid

Answer 8

raising the temperature of solution

Question 9

buffer question - X added to buffer sol

Answer 9

conc/mol of HA and A-/H+
conc/mol of X
if X = acid then HA + X
if X = base then HA - X

Question 10

mol

Answer 10

conc x vol

mass / mr

Question 11

pH of buffer sol changes slightly compared to water

Answer 11

The H+ gets absorbed by the A- instead of reacting with water to form H+

Question 12

SA - SB

Answer 12

pH eq is 7 takes up most of graph

Question 13

SA - WB

Answer 13

pH eq is below 7

Question 14

WA - SB

Answer 14

pH eq is above 7

Question 15

WA - WB

Answer 15

pH eq around 7 squiggly line

Question 16

acid added to base

base added to acid

Answer 16

backwards S

S

Question 17

strong acid examples

Answer 17

hydrochloric acid - HCl
sulfuric acid - H2SO4
nitric acid - HNO3

Question 18

weak acid examples

Answer 18

carboxylic acids

Question 19

strong base examples

Answer 19

sodium hydroxide - NaOH
potassium hydroxide - KOH
calcium hydroxide - Ca(OH)2
barium hydroxide - Ba(OH)2

Question 20

weak base examples

Answer 20

ammonia - NH3

amines

Question 21

ethanoic acid vs ethanedioic acid

Answer 21

1) both acids have RCOOH structure
A] ethanoic acid R = CH3
B] ethanedioic acid R = COOH

A] CH3 = positive inductive effect
so… no effect on O-H polarity

B] O’s are very electronegative
COOH = negative inductive effect
so… O–H bond is more polarised
so…. more dissociation into H+ ions

2) ethanedioic acid is stronger than ethanoic acid

Question 22

chloroethanoic acid > ethanoic acid

Answer 22

Cl has negative inductive effect

makes O-H more polar

Question 23

buffer when acid/alkali added

Answer 23

acid = incr in concentration of H+ ions, equilibrium moves to the left
alkali = OH- reacts with H+ ions, equilibrium moves to the right to replace the H+ ions
concentration of H+ remains constant

Question 24

if acid dissociation = endo

pH if sol is heated

Answer 24

pH decreases
eq moves to right/more dissociation
to oppose incr in temp

Question 25

ammonia vs ethylamine

Answer 25

ethylamine stronger alkyl group = positive inductive effect incr ability to accept H+

Question 26

equivalence point

Answer 26

acid mol = base mol

Question 27

half equivalance point

Answer 27

pka = pH