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What is a Bronsted-Lowry acid?
proton donor
What is a Bronsted-Lowry base?
proton acceptor
What is a weak acid
An acid that is only partially ionised in aqueous solution
What is a strong acid
An acid that completely dissociates in aqueous solution
Explain what is meant by a weak Bronsted-Lowry acid
A weak acid that partially dissociates in aqueous solution. It is in equilibrium with its H+ and A- ions or HA(aq) ⇌ H+(aq) + A-(aq)
Write down an expression for the ionic product Kw for water
Kw = [H+] [OH-]
[H+] =
[H+] = 10^-pH
pH =
-log [H+]
What information is provided by Ka values
The acid strength
What is a Monobasic acid
1 H+ ion can be replaced per molecule in an acid base reaction. The replacement would typically be a metal ion or ammonium ion
E.g HCl
What is a dibasic acid
Can have two protons replaced when they react with bases
H2SO4 + 2NaOH -> 2H2O + NaSO4
Give an example of a tribasic acid
Phosphoric acid
What is a conjugate acid base pair
A pair of two species that transform into each other by gain or loss of a proton
Ka =
[H+][A-]/[HA]
What is the ionic product of water?
Define the term transition element
A transition element forms at least 1 ion with a partially filled d orbital
What is meant by a bidentate ligand
A ligand which donates 2 electron pairs to a transition metal ion
To form 2 coordinate/ dative covalent bonds
What are physical properties of transition metals
*Dense
*Durable
* High tensile strength
* high bp and mp
What are chemical properties of transition elements
*Good catalysts
*Form coloured compounds
*Form compounds with variable oxidation states
What is a ligand
A ligand donates an electron pair to a transition metal ion forming coordinates/ dative covalent bonds
What is a complex ion
A transition metal ion bonded to one or more ligands by coordinate bonds
What are catalysts?
Catalysts lower the activation energy by providing an alternative pathway that lowers the activation energy
one lone pair is
monodentate ligands
two lone pair is
bidentate ligand
six lone pair is
hexadentate ligands
what is the coordination number
the total number of coordinate bond formed between a central metal ion and its ligand
if there are two coordinate bonds the shape is...
linear
if there are four coordinate bonds the shape is...
tetrahedral with a bond angle of 109.5 or square planar with a bond angle of 90 degrees
if there are six coordinate bonds the shape is...
octahedral with a bond angle of 90 degrees
what are steroisomers
the same structural formula but a different arrangements of the atoms in space
Complex ions can display two types of stereoisomerism:
cis-trans isomerism and optical isomerism
where does optical isomerism only occur
optical isomerism only occurs in octahedral complexes containing two or more bidentate ligands.
What are optical isomers?
optical isomers called enantiomers are non-superimposable mirror images of each other
what is interesting about trans isomers
trans isomers cannot form optical isomers as a mirror image as it is exactly the same and can be superimposed
what is a ligand substitution reaction
A reaction in which one ligand in a complex ion is replaced by another ligand
what is the overall shape of haemoglobin
octahedral with a bond angle of 90 degrees
What colour is [Cu(H2O)6] 2+ solution
pale blue
what colour is [Cu(NH3)4(H2O)2] 2+ solution
dark blue
what colour is [CuCl4] 2- solution
yellow
what colour is[Cr(H2O)6] 3+ solution
violet
what colour is [Cr(NH3)6] 3+ solution
purple
[Cu(H2O)6] 2+ + 4NH3 ⇋
[Cu(NH3)4(H2O)2] 2+ + 4H2O
[Cu(H2O)6] 2+ + 4Cl- ⇋
[CuCl4] 2- + 6H2O
[Cr(H2O)6] 3+ + 6NH3 ⇋
[Cr(NH3)6] 3+ + 6H2O
What is the formula of the precipitates and the colour changes between NaOH and Cu 2+
Blue solution forms blue precipitate
Cu(OH)2
What is the formula of the precipitates and the colour changes between NaOH and Fe 2+
Pale green to dark green precipitate
brown on standing in air
Fe(OH)2
What is the formula of the precipitates and the colour changes between NaOH and Fe 3+
pale yellow solution forms orange-brown precipitate
Fe(OH)3
What is the formula of the precipitates and the colour changes between NaOH and Mn 2+
pale pink solution forms a light brown precipitate that darkens on standing in air
Mn(OH)2
What is the formula of the precipitates and the colour changes between NaOH and Cr 3+
violet solution forms a grey-green precipitate
Cr(OH)3
What is the formula of the precipitates and the colour changes between excess NaOH and Cu 2+
No change - precipitate is insoluble in excess
What is the formula of the precipitates and the colour changes between excess NaOH and Fe 2+
No change - precipitate is insoluble in excess
What is the formula of the precipitates and the colour changes between excess NaOH and Fe 3+
No change - precipitate is insoluble in excess
What is the formula of the precipitates and the colour changes between excess NaOH and Mn 2+
No change - precipitate is insoluble in excess
What is the formula of the precipitates and the colour changes between excess NaOH and Cr 3+
precipitate dissolves in excess to form a dark green solution
[Cr(OH)6] 3-
What is the formula of the precipitates and the colour changes between NH3 and Cu 2+
Blue solution forms a blue precipitate
Cu(OH)2
What is the formula of the precipitates and the colour changes between NH3 and Cr 3+
violet solution forms a grey- green precipitate
Cr(OH)3
What is the formula of the precipitates and the colour changes between excess NH3 and Cu2+
dark blue solution - ligand exchange
[Cu(NH3)4(H2O)2] 2+
What is the formula of the precipitates and the colour changes between excess NH3 and Cr 3+
purple solution - ligand exchange
[Cr(NH3)6] 3+
what metal ions react with NH3 in the same way as they do with NaOH
Fe 2+
Fe 3+
Mn 2+
