acids Flashcards
acid + metal
= salt + hydrogen
acid + metal oxide
=salt + water
acid + metal hydroxide
=salt + water
acid + metal carbonate
= salt + co2 + water
ammonia + hydrochloric acid =
NH4CL(aq)
type of acid used and salt formed
hydrochloric - chloride (cl-)
sulfuric - sulfate (SO42-)
nitric - nitrate (NO3-)
phosphoric - phosphate (PO43-)
ethanoic - ethanoate (CH3COO-)
definition of an acid
proton donor
monoprotic / diprotic
monoprotic acids release 1 H+
diprotic acids release 2 H+
definition of a base
a base is a proton acceptor
will accept and bind to H+
water
water can act as a base or an acid so amphoteric
strong acids
fully dissociates
equilibrium lies entirely to the right hand side
so if original conc of strong acid is x when it fully dissociates the conc of H+ will now be x
equation of PH
PH = -Log10[H+]
weak acids
partially dissociate
position of equilibrium is way over to the left hand side - cant work out concentration H+
examples of strong acids
HCl
H2SO4
HNO3
H3PO4
Ka
used to figure out amount of H+ ions that have partially dissociated
higher Ka - more dissociated
ka expression example
eg HCOOH(aq) <-> HCOO-(aq) +H+(aq)
Ka = [H+] [HCOO-] / [HCOOH]
[H+] = [HCOO-]
Ka = [H+] ^2 / [HCOOH]
rearrange to find [H+]
PKa=
pKa = -Log10Ka
Kw
Kw ionic product of water
alters with temp
Kw = [H+] [OH-] —– Kw = [H+]^2
grouped together as Kc and [H20] are constants
pure water is neutral
[H+] = [OH-]
Kw value at 298K
1x10-14
water dissociation
Temp rise
forward reaction is endothermic
at temperatures of 298K the equilibrium shifts to the right to oppose the temperature rise
this means that [H+] increase
strong bases
fully dissociate to release OH- ions
position of equilibrium lies entirely to the right hand side
USE KW
Kw=[H+][OH-]
[OH-] = conc of base as fully dissociates
method for PH titrations
1-measure the PH of the acid solution and record
2-add 1cm3 of the base solution
3-stir the mixture
4-measure the ph and record
5-repeat the process until the base is in excess
6-add base in smaller increments near the end point
why should you calibrate the ph meter
important to calibrate as after storage it may not give an accurate reading
to calibrate it you place the ph meter in a solution of known ph and then adjust the meter accordingly
