past paper questions Flashcards
(17 cards)
in terms of electrons explain why copper chloride aqueous has a green colour
-absorbs certain frequencies of white light
-d electrons get excited and move between orbitals
-green light wasn’t absorbed, so it is the one we see.
define ligand
a ligand is an ion or a molecule that donates a lone pair of electrons to form a co-ordinate bond with a transition metal
define bidente
a bidente ligand forms two co-ordinate bonds to a transition metal through two different atoms on the same ligand
define complex
a complex is a central metal or ion surrounded by ligands joined by co-ordinate bonds.
define co-ordination number
the number of co-ordinate bonds to the central metal.
what is a co-ordinate bond
a covalent bond where both electrons come from one atom
explain why V2+ has a pH of 5 and why V3+ has pH of 2
-V3+ has a greater charge density
-therefore greater polarising effect on O-H bonds.
with reference to the reactants on the haber process, explain how a reaction on this hetergenous catalyst takes place
-Nitrogen and hydrogen adsorb onto the surface of the solid iron catalyst.
-Their bonds are weakened, allowing them to react more easily to form ammonia.
-The ammonia then desorbs from the surface.
Along with redox, potassium iodide can undergo another type of reaction
with sulphuric acid. Write an equation to show this type of reaction.
2KI + H2SO4 → K2SO4 + 2HI
what is the test for ammonium ions
-heat with aqueous NaOH
-which produces ammonia (alkaline gas)
-to confirm its ammonia litmus paper should turn blue
Explain what is meant by the fingerprint region of an infra-red spectrum.
State how it is used to confirm the identity of organic molecules such as the primary,
secondary and tertiary alcohols of molecular formula C4H10O.
-Region 1500–400 cm–1
-exact match to spectrum of known compound
1.3 State three different features of transition metal complexes that cause a change in the value of ΔE, the energy change between the ground state and the excited state of the d electrons.
- (Identity of the) metal
- Charge (on the metal) / oxidation state
/ charge on complex - (Identity of the) ligands
- Co-ordination number / number of
ligands - Shape
define the terms bronsted-lowry acid and lewis acid
Brønsted-Lowry acid: A proton or H+ donor
Lewis acid: A lone or electron pair acceptor
write an equation to show how aqueous chromium (iii) chloride acts as an acid
Cr(H2O)6]3+ + H2O → [Cr(H2O)5(OH)]2+ + H3O+
why is TMS added to all samples
-non toxic
-inert
-gives one peak by 1H or 13C NMR as all H s are in the same environment aswell as Cs on theirs.
how is NMR carried out
1)sample dissolved ina volatile solvent so no H atoms present. polar solvent=D2O OR CDCl3. non polar solvent = CCl4
2)add a standard (and TMS added to all samples)
3)then carry out either 13C NMR or 1H NMR
why is D used instead of H in the solvent
-nucleus of H: has 1 proton which is odd number so is magnetic –>is NMR active –>produces signal–> interferes with spectrum
-nucleus of D: has 1 proton + 1 neutron so even number so is NOT magnetic –> NMR not active –> doesnt produce signal –> doesmt interfere with spectrum
