chapter 20 Flashcards
what do acids do in water?
dissociate and release H+ ions into solution
what do alkalis do in water?
dissolves in water and releases OH- ions
what is a neutralisation reaction?
when an acid reacts with a base to produce salt and water
what is something important about ionic equations?
contains only ions that take part in the reaction
anything s/l/g goes into the equation
what does a metal + acid produce?
salt + H2
M A S H
what is a bronsted-lowry acid?
proton/H+ donor
what is a bronsted-lowry base?
proton/H+ acceptor
What is a conjugate acid-base pair?
Contains 2 species
Can be interconverted by transfer of a proton
What happens during dissociation?
Only takes place when water is present
Acids donate protons to water to form hydronium ion
what are strong acids?
completely dissociate in aqueous solutions
what are weak acids?
partially dissociate in aqueous solutions
what is pH?
measure of concentration of H+ ions in a solution
or
-log [H+]
what does the smaller the pH mean?
the more acidic/larger concentration of H+
what is the assumption for strong monobasic acids?
[HA] = [H+]
what is the Ka equation?
Ka = [H+][A-]/[HA]
what is the equation for pKa?
-logKa
how do you find Ka from pKa?
10^-pKa
what is the assumptions for weak acids?
[H+] = [A-]
[HA]eqm = [HA]start
what is the assumed equation for Ka for weak acids?
Ka = [H+]^2/[HA]
what are the limitations of the approx [H+]=[A-]?
if pH>6 then [H+] from dissociation of water becomes more significant
approx breaks down for very weak acids
what are the limitations of the approx [HA]eqm=[HA]start?
breaks down when [HA]eqm becomes more significant
not justified for stronger weak acid
can water be both an acid and base?
water ionises very slightly so can act as both an acid and a base
what is the equation for Kw?
Kw = [H+][OH-]
when water is neutral what are the concentrations of H+ and OH- ions?
[H+] = [OH-]
what does Kw do?
controls concentrations of H+ and OH- in a solution
how is pH of a strong base calculated?
concentration of base
ionic product of water Kw
how do you calculate the new concentration of a solution?
original conc x volume of reagent/total volume
