2.3 acid-base and redox reactions Flashcards
acids vs bases (alkali = soluble base)
acids = proton donors, produce H+ ions
bases = proton acceptors, produce OH- ions
what type of reaction when acids and bases react with water?
when acids and bases react with water they form a reversible reaction
weak acid
e.g. carboxylic acids
partially dissociate in solution
backwards reaction favoured, not many H+ ions produced (small % of products will be ions)
strong acid
e.g. HCl, H2SO4, HNO3
fully dissociate in solution
forwards reaction favoured, lots of H+ produced
strong base
e.g. NaOH, KOH
fully dissociate in solution
forwards reaction favoured, lots of OH- ions produced
weak base
e.g. NH3
partially dissociate in solution
backward reaction is favoured, not many OH- ions produced (small % of products will be ions)
polyprotic acid
acid that donates more than one proton
monoprotic acid
nitric acid (HNO3)
1 mole of HNO3 will produce 1 mole of H+ ions
diprotic acid
sulphuric acid (H2SO4)
1 mole of H2SO4 will produce 2 moles of H+ ions
triprotic acid
phosphoric acid (H3PO4)
1 mole of H3PO4 will produce 3 moles of H+ ions
neutralisation ionic equation
H+(aq) + OH-(aq) <–> H2O(l)
ammonia anomaly rule when reacting with water
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)
metals reacting with acids
metal + acid -> salt + hydrogen
e.g.
Ca(s)+H2SO4(aq) -> CaSO4(aq)+H2(g)
Ca(s) + 2H+(aq) -> Ca2+(aq) + H2(g)
metal oxides reacting with acids
metal oxide + acid -> salt + water
e.g.
MgO(s)+2HCl(aq) -> MgCl2(aq)+H2O(l)
MgO(s) + 2H+(aq) -> Mg2+(aq) + H2O(l)
metal hydroxides reacting with acids
metal hydroxide + acid -> salt + water
e.g.
2NaOH(aq)+H2SO4(aq) -> Na2SO4(aq)+2H2O(l)
2OH-(aq) + 2H+(aq) -> 2H2O(l)
metal carbonates reacting with acids
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)
what are titrations used for?
to work out the concentration of an acid or alkali
basic set up of titration
- have acid or alkali with known conc in burette
- have acid or alkali with unknown conc but known volume in conical flask - few drops of indicator
- add chemical in burette to conical flask until indicator changes colour, drop by drop near end point - known as end point
concordant results
results that are concordant are within 0.10cm3 of each other
how do you prepare a standard solution?
- WEIGH solute (solid) precisely using balance
- TRANSFER solid from weighing boat to beaker, wash solid left with distilled water
- DISSOLVE solid fully using distilled water, stir ensuring fully dissolved
- TRANSFER solution to volumetric flask using funnel, rinse beaker using distilled water and glass rod in flask
- FILL using more distilled water to fill to graduation line
- MIX by inverting volumetric flask a few times, make sure there is a lid on
reduction and oxidation
reduction is gain of electrons (decrease in oxidation number)
oxidation is loss of electrons (increase in oxidation number)
redox reaction
when reduction and oxidation takes place simultaneously in a reaction
reducing agents
causes another atom to be reduced by being oxidised themselves (losing electrons)
oxidising agents
causes another atom to be oxidised by being reduced themselves (gaining electrons)
systematic name of ClO-
chlorate(III)
because…
O = -2 (-2 x 2 = -4)
overall charge is -1
-1 - -4 = +3
O= -4 Cl= +3
