UNIT 1 Section 10 - Acids, Bases and pH Flashcards
define a bronsted lowry acid
proton donor
define a bronsted lowry base
proton acceptor
write an equation for the ionisation of water to from H+ ions
H2O <—-> H+ + OH-
write an equation for the ionisation of water to produce a hydroxonium ion
2H2O <—-> H3O+ + OH-
what is the equation for Kw
Kw= [H+][OH-]
what is the value of Kw at 289K
1x10-14
what physical factors affect the value of kw and how
temperature
if the temperature is increased the equilibrium shifts to the right so Kw increases and the pH decreases
why is pure water still neutral is the pH isnt 7
the concentration of H+ is still equal to the concentration of OH-
what is the expression for pH
pH=-log10[H+]
if two solutions have a difference of 1 what is the difference in [H+]
a factor of 10
what is the expression of [H+] from pH
[H+] = 10-pH
what is the difference when finding [H+] from the concentration of diprotic and triprotic acids
need to multiply the concentration of the acid by the number of protons
define the term strong acid
one which fully dissociates in water
define the term strong base
one which fully dissociates in water
what is a weak acid and base
weak acids and bases do not fully dissociate in water and only partially dissociate into their ions
give examples of strong acids
HCL, H2SO4,H3PO4
give some examples of strong bases
NaOH, CaCO3, Na2CO3
give some examples of weak acids
CH3COOH
give an example of a weak base
NH3
what is the expression for Ka
Ka = [H+][A-]/[HA]
what is a titration
teh addition of an acid or base of a known concentration to an unknown base or acid to determine the concentration of the unknown acid or base
define the term equivalence point
the point where the exact volume of base has been added to neutralise the acid or vice versa
what generally happens to the pH of a solution around the equivalence point
there is a large and rapid change in pH except in weak acid and weak base titration
what is the end point
when the indicator just changes colour
what are the properites of a good indicator for a reaction
sharp colour change
end point must be the same as the equivalence point
distinct colour change
what indicator would you use for a strong acid-base titration
Phenolphthalein
what indicator would you use for a strong-acid weak base titration
methyl orange
what indicator would you use for a strong base-weak acid titration
phenolphthalein
what indicator would you use from a weak acid and weak base titration
neither work
what colour is methyl orange in and acid and colour in an alkali and what pH does it change
red in acid
yellow in alkali
4-5
what colour is phenolphthalein in and acid and colour in an alkali and what pH does it change
colourless in acid
red in alkali
9-10
what is the half neutralisation point
when the volume = half the volume that has been added at the equivalence point
draw a strong acid base graph
refer to booklet
draw a strong acid weak base graph
refer to booklet
draw a weak acid strong base graph
refer to booklet
draw a weak acid and weak base graph
refer to booklet
