Acids And Bases Flashcards
Why is pure water neutral ?
Conc of H+ ions = Conc of OH- ions
Definition of Bronsted- lowery acid
Proton donor
Bronsted-lowery base
Proton acceptor
Equation for pH
pH= -log[H+]
Equation for [H+] using pH
[H+]= 10^-pH
Equation for Kw
Kw= [H+][OH-]
Kw of pure water
Kw= [H+]^2
Effect of temperature increase on pH and neutrality of water
Increase in temp= equilibrium shifts right to lower temp
More [H+] and [OH-]
Kw and pH increase
Still neutral
Calculating pH of strong bases
Conc of OH- equal to conc of solution
[H+] = Kw / [OH-]
pH= -log[H+]
Reactions between strong acids and strong bases
Mol of H+ = conc x vol
Mol of OH- = conc x vol
Mol excess = H+ mol - OH- mol or visa versa
Conc excess = mol excess / total new volume
pH= -log[H+] or [H+] = Kw / [OH-]
General chemical equation of strong acid
HX = H+ + X-
Strong acids to know
HCl
HNO3
H2SO4
Weak acids to know
Carboxylic acids
Strong bases to know
NaOH
KOH
Ba(OH)2
Weak bases to know
Ammonia
Equation for Ka (acid dissociation constant)
Ka= [H+][A-] / [HA]
Equation for pKa
pKa = -log(Ka)
Ka of weak acids in aqueous solution with nothing else added
Ka = [H+]^2 / [HA]
calculating the volume of an acid
calculate [H+] from pH
calculate moles of HCl (mol x conc)
vol = mole HCl / [H+]
what does the phrase “fully dissociates” tell you about the nature of an acid
it is a strong acid
calculating the pH of a diluted acid
Calculate [H+] = (initial vol/ total new vol) x conc
pH = -log[H+]
general value of Kw
1.00 x 10-14 mol^2 dm^-6
explain why chloroethanoic is a stronger acid than ethanoic acid
chlorine is electronegative and so withdraws electrons, making OH bond more polar thus H+ is more easily lost
explain why data books so not usually contain values of Ka for strong acids
Ka value for a strong acid is very high/ infinite
why would the pH of magnesium hydroxide be lower than that of calcium hydroxide
it is less soluble
