acids and bases

Question 1

pH

Answer 1

The pH of a solution is a measure of its hydrogen ion concentration and thus its acid-base characteristics. High hydrogen ion concentration, that is an acidic solution, corresponds to a low pH. Basic solutions have a high pH. Pure water is neutral and has a pH of seven. Dissolving an acid or base in water will change his pH. Adding an acid raises the concentration of hydrogen ions thus Lowering the pH. Adding a base to water raises the hydroxide ion concentration and causes the hydrogen ion concentration to fall causing the pH to rise.

Question 2

arrhenius theory: acids

Answer 2

an acid is a substance that will ionise in a solution producing H+ (aq) ions.

Question 3

arrhenius theory: bases

Answer 3

A base is a substance that will dissociate in solution releasing OH- (aq) ions

Question 4

acids: oxides

Answer 4

non-metal oxides

Question 5

bases: oxides

Answer 5

metal oxides/hydroxides

Question 6

ionisation

Answer 6

Acids have a covalent molecular structure and so don’t actually contain hydrogen ions. However, when dissolved in the water they produce hydrogen ions in a reaction called ionisation. This will result in the formation of hydrogen ions

Question 7

dissociation

Answer 7

Bases are all ionic hydroxide compound. These compounds contain metal ions and hydroxide ions. When dissolved in water these ions are released into solution. This process is called dissociation

Question 8

strong acids

Answer 8

Arrhenius theory States that strong acids dissolve in water to undergo complete ionisation. Thus all the dissolved acid converts into ions. A single arrow in the ionisation equation shows this.

Question 9

strong acids vs weak acids

Answer 9

always produce a more vigorous reaction than weak acids
a strong acid will produce a higher hydrogen ion concentration than weak acids

Question 10

weak acid

Answer 10

the theory identifies a weak acid as one that undergoes partial ionisation which means that the remaining is mostly in the form of unionised molecules. Double arrows show the partial nature of this reaction.

Question 11

strong acids: examples

Answer 11

• HCl (hydrochloric acid)
• H2SO4 (sulfuric acid)
• HNO3 (nitric acid)

Question 12

weak acids: examples

Answer 12

• CH3COOH (ethanoic acid)
• C6H8O7 (citric acid)
• H2CO3 (carbonic acid)
• H3PO4 (phosphoric acid)
• H2SO3 (sulfurous acid)
• HSO4- (hydrogen sulfate ion)

Question 13

strong bases

Answer 13

strong bases are group 1 or 2 metal oxides/hydroxides
- NaOH (sodium hydroxide)
- Ca(OH)2 (calcium hydroxide)
- MgO (magnesium oxide)

Question 14

weak bases

Answer 14

• CuO (copper (II) oxide)
• NH3 (ammonia)
• NaHCO3 (sodium hydrogencarbonate)

Question 15

acids: characteristics

Answer 15

• tastes sour
• cause indicators to change colour to red
• are corrosive
• many solutions of acids conduct electricity
• reacts with carbonates to form carbon dioxide and water
• react with some metals to form hydrogen
• react with bases to form bases

Question 16

bases: characteristics

Answer 16

• taste bitter
• feel slippery
• cause indicators to change colour to blue
• can be corrosive
• do not react with most metals
• many solutions of bases conduct electricity
• react with acids to form water

Question 17

conjugate

Answer 17

acid:
loss of H+
HCl -> Cl- (conjugate base)

base:
gain of H+
NH3 -> NH4+ (conjugate acid)

Question 18

electrolytes

Answer 18

solutions of ions

Question 19

strong electrolytes

Answer 19

def: completely ionises
strong electrolytes have all dissolved molecules ionise in solution, there are no molecules left only ions present in water

Question 20

examples of strong electrolytes

Answer 20

all ionic compounds (what does dissolve goes into ions), if insoluble will still be a strong electrolyte but will have low conductivity

strong acids and strong bases: SA: HCl, HNO3, H2SO4, SB: group 1 and group 2 metal oxides and hydroxides

Question 21

weak electrolytes

Answer 21

definition: partially ionises, only some dissolved molecules ionise in solution, there will be neutral molecules and some ions present in the water

Question 22

examples of weak electrolytes

Answer 22

weak acids and bases:
WA: CH3COOH, H3PO4, H2CO3, WB: NH3

Question 23

non-electrolytes

Answer 23

definition: doesn’t ionise, all remain as neutral species in solution

Question 24

examples of non-electrolytes

Answer 24

most covalent substances that aren’t acids or bases e.g. sugar (C6H12O6), sucrose, kerosene and ethanol

Question 25

hydronium ion

Answer 25

H3O+ is an ion that is formed through the protonation of water
H2O + H+(ion) → H3O+