2.3 acid-base and redox reactions

Question 1

acids vs bases (alkali = soluble base)

Answer 1

acids = proton donors, produce H+ ions
bases = proton acceptors, produce OH- ions

Question 2

what type of reaction when acids and bases react with water?

Answer 2

when acids and bases react with water they form a reversible reaction

Question 3

weak acid

Answer 3

e.g. carboxylic acids
partially dissociate in solution
backwards reaction favoured, not many H+ ions produced (small % of products will be ions)

Question 4

strong acid

Answer 4

e.g. HCl, H2SO4, HNO3
fully dissociate in solution
forwards reaction favoured, lots of H+ produced

Question 5

strong base

Answer 5

e.g. NaOH, KOH
fully dissociate in solution
forwards reaction favoured, lots of OH- ions produced

Question 6

weak base

Answer 6

e.g. NH3
partially dissociate in solution
backward reaction is favoured, not many OH- ions produced (small % of products will be ions)

Question 7

polyprotic acid

Answer 7

acid that donates more than one proton

Question 8

monoprotic acid

Answer 8

nitric acid (HNO3)
1 mole of HNO3 will produce 1 mole of H+ ions

Question 9

diprotic acid

Answer 9

sulphuric acid (H2SO4)
1 mole of H2SO4 will produce 2 moles of H+ ions

Question 10

triprotic acid

Answer 10

phosphoric acid (H3PO4)
1 mole of H3PO4 will produce 3 moles of H+ ions

Question 11

neutralisation ionic equation

Answer 11

H+(aq) + OH-(aq) <–> H2O(l)

Question 12

ammonia anomaly rule when reacting with water

Answer 12

ammonia reacts with acids to make ammonium salts but NO water
*ammonia does not produce OH- ions directly. it reacts with water first and accepts a proton to produce ammonium ions (NH4+) and OH- ions
NH3(aq) + H2O(l) <–> NH4+(aq) + OH-(aq)

Question 13

metals reacting with acids

Answer 13

metal + acid -> salt + hydrogen
e.g.
Ca(s)+H2SO4(aq) -> CaSO4(aq)+H2(g)
Ca(s) + 2H+(aq) -> Ca2+(aq) + H2(g)

Question 14

metal oxides reacting with acids

Answer 14

metal oxide + acid -> salt + water
e.g.
MgO(s)+2HCl(aq) -> MgCl2(aq)+H2O(l)
MgO(s) + 2H+(aq) -> Mg2+(aq) + H2O(l)

Question 15

metal hydroxides reacting with acids

Answer 15

metal hydroxide + acid -> salt + water
e.g.
2NaOH(aq)+H2SO4(aq) -> Na2SO4(aq)+2H2O(l)
2OH-(aq) + 2H+(aq) -> 2H2O(l)

Question 16

metal carbonates reacting with acids

Answer 16

metal carbonate + acid -> salt + carbon dioxide + water
e.g.
Li2CO3(s)+2HNO3(aq) -> 2LiNO3(aq)+CO2(g)+H2O(l)
Li2CO3(s) + 2H+(aq) -> 2Li+(aq) + CO2(g) + H2O(l)

Question 17

what are titrations used for?

Answer 17

to work out the concentration of an acid or alkali

Question 18

basic set up of titration

Answer 18

1. have acid or alkali with known conc in burette
2. have acid or alkali with unknown conc but known volume in conical flask - few drops of indicator
3. add chemical in burette to conical flask until indicator changes colour, drop by drop near end point - known as end point

Question 19

concordant results

Answer 19

results that are concordant are within 0.10cm3 of each other

Question 20

how do you prepare a standard solution?

Answer 20

1. WEIGH solute (solid) precisely using balance
2. TRANSFER solid from weighing boat to beaker, wash solid left with distilled water
3. DISSOLVE solid fully using distilled water, stir ensuring fully dissolved
4. TRANSFER solution to volumetric flask using funnel, rinse beaker using distilled water and glass rod in flask
5. FILL using more distilled water to fill to graduation line
6. MIX by inverting volumetric flask a few times, make sure there is a lid on

Question 21

reduction and oxidation

Answer 21

reduction is gain of electrons (decrease in oxidation number)
oxidation is loss of electrons (increase in oxidation number)

Question 22

redox reaction

Answer 22

when reduction and oxidation takes place simultaneously in a reaction

Question 23

reducing agents

Answer 23

causes another atom to be reduced by being oxidised themselves (losing electrons)

Question 24

oxidising agents

Answer 24

causes another atom to be oxidised by being reduced themselves (gaining electrons)

Question 25

systematic name of ClO-

Answer 25

chlorate(III)
because…
O = -2 (-2 x 2 = -4)
overall charge is -1
-1 - -4 = +3
O= -4 Cl= +3