Need To Know Flashcards
electronegativity
the ability of an atom to attract the pair of electron in a covalent bond
what factors affect electronegativity
CRAM
charge raidus attraction and shielding ie
Cl2 AND WATER HYDROCHLORIC ACID and chloric acid
Cl2 + H2O –> 2H+ + CL- + HClO + ClO-/HCl
relative atomic mass
Mean mass of one atom /
1/12 mass of one atom of C12
whats makes a tranistion metal and what it defing feutures?
incomplete d subshell forms colour ions variable oxidation state catlystic abilities complex formations
whats a ligand (bidentate lingand)
(2) atom dontates a (2) lone pair and forms (2) co-od bond
why is reaction feable for transition metals changing chelate effect/.
more moles in products = increasing entropy
same no. bond broken and formed enthalpy change small
there gibs freee energy is negative as small number ets
4 shapes of transition metals
any comon octohedral
cl- ligand tetrahedral
pt as metal square [lanar
ag metal linear
trans isomerism in cisplatin and an octahdral
basic knowldege hoe
optical isomers tm
octerhedral with 3x bidentate ligand
what causes colour change in anion metal thing
change in oxidation state
co oc no.
ligand
change in shape
equations which link the colour, wavelength and
frequency of the light absorbed with the energy
differ beteeen split orbitals
ΔE = hv or ΔE = hc/λ v = frequency of light absorbed (unit s-1 or Hz) H = Planck’s constant 6.63 × 10–34 (J s) E = energy difference between split orbitals (J) c = speed of light 3.00 x 108 (m s–1) λ = wavelength of light absorbed (m)
VO2 + Oxidation state +5
VO 2+ Oxidation state + 4
V3+ Oxidation state + 3
V2+ Oxidation state + 2
Yellow
blue
green
violet
what do u need to know about EDTA4 as a ligand
EDTA4- can form six coordinate bonds; two coordinate bonds form from the N atoms, and four coordinate bonds form the O- atoms.
What do you need to know about haemoglobin
O2 forms a co-ordinate bond to Fe2+ in haemoglobin enabling oxygen to be transported in the blood.
CO is toxic because CO bonds more strongly to the Fe2+ in haemoglobin.
This prevents O2 from bonding to the Fe2+, causing suffocation.
big e biv abs and small e roy abs
hint- roygibiv
Big E BIV abs
If a transition metal compound has LARGE ∆E between d sub-shells:
- High energy light (i.e. Violet, Indigo and Blue)
- will be absorbed to excite the electrons
- Red, Orange, Yellow light will be reflected
- This means the compound will look Red/Orange
Small E ROY abs
If a transition metal compound has SMALL ∆E between d sub-shells:
- Low energy light (i.e. Red, Orange, Yellow)
- will be absorbed to excite the electrons
- Blue, Indigo, Violet) will be reflected by the compound
- This means the compound will look Blue/Purple
Colour of [Fe(H2O)6]2+ [Fe(H2O)6]3+ [Cr(H2O)6]2+ [Cr(H2O)6]3+ [Co(NH3)6]2+ [Co(NH3)6]3+
[Fe(H2O)6]2+ Green [Fe(H2O)6]3+ Pale Brown
[Cr(H2O)6]2+ Blue
[Cr(H2O)6]3+ Red-Violet
[Co(NH3)6]2+ Brown [Co(NH3)6]3+ Yellow
How can colorimetry be used to determine unkown conc of a tm
(1) An appropriate ligand (such as -SCN) is added to the solution in order to intensify the colour.
(2) A range of solutions of the same complex ion are made of known concentrations.
(3) One at a time these are tested in a colorimeter and the transmission (or absorbance) is measured.
(4) A graph is plotted of Conc vs Transmission (or absorbance) and a line of best fit drawn.
(5) The transmittance/ absorbance of the unknown solution is measured in a colorimeter, and its concentration is determined by reading off the calibration curve.
WHAT IS CTALYST
HOW DOES IT WORK
- -A substance which increases the rate of a chemical reaction AND Without being used up
- Provide an alternative reaction pathway AND With a lower activation energ
Heterogenous catalyst vs homogeneous catalysts
Heterogeneous – where the catalyst is in a different phase to the reactants
Homogeneous – where the catalyst is in the same phase as the reactants
how does Heterogeneous Catalysis work?
why more effiecient?
(1) Reactants adsorb onto the surface of the catalyst on an active site.
(2) Reaction occurs on the surface of the catalyst
(3) Products desorb from the surface if the catalyst
- Increase the surface area
- Spread the catalyst over an inert support medium.
catalyst poising?
poisoning can occur:
- Impurities can block the active sites.
- This prevents the reactants from adsorbing
- Purifying the reactants is the best way to prevent poisoning.
heterogenous catalyst process you need to know?
(1) Making Ammonia in the Haber Process Catalysed by solid IRON
N2(g) + 3N2(g) 2NH3(g)
(2)Making Sulfuric Acid in the Contact Process. Catalysed by solid Vanadium (V) Oxide – V2O5
Step 1 – Sulfur Dioxide is oxidised to Sulfur Trioxide
SO2(g) + V2O5(s) SO3(g) + V2O4(s)
Step 2 – The Vanadium (IV) Oxide is then converted back to Vanadium (V) Oxide with oxygen.
2V2O4(s) + O2(g) 2V2O5(s)
This means the overall reaction is:
2SO2(g) + O2(g) -> 2SO3(g)
Sulfuric Acid is then formed by reacting SO3 with H2O.
(3)Manufacture of Methanol
Firstly this reaction forms a mixture known as synthesis gas
CH4(g) + H2O(g) -> CO(g) + 3H2(g)
Then the following reaction is catalysed by solid Chromium (III) Oxide – Cr2O3
CO(g) + 2H2(g) -> CH3OH(g)
Homogeneous catalyst example you MUST know?
S2O82-(aq) + 2I-(aq) -> 2SO42-(aq) + I2(aq)
The uncatalyzed reaction has a high Ea as the two negative ions repel each other:
S2O82-(aq) + 2I-(aq) -> 2SO42-(aq) + I2(aq)
This reaction is catalysed by Fe2+ ions in a two-step process.
Step 1: S2O82-(aq) + 2Fe2+(aq) -> 2SO42-(aq) + 2Fe3+(aq)
Step 2: 2I-(aq) + 2Fe3+(aq) –> I2(aq) + 2Fe2+(aq)
Both steps now involve reactions between positive and negative ions
In the second step the Fe2+ catalyst is regenerated.
Fe3+ could also be used as a catalyst, as step 2 could occur before
