paper 3

Question 1

why do polar bonds exist

Answer 1

becauase O/N atom is significantly more electronegative than carbon/hydrogen

Question 2

units of activation energy

Answer 2

J mol -1// kJ mol -1

Question 3

how to calculate total percentage uncertainty

Answer 3

The total percentage uncertainty is calculated by adding together the percentage uncertainties for each measurement.

Question 4

appearance of halogens in their natural state

Answer 4

F2 - pale yellow gas
Cl2 - pale green gas
Br2 - orange/brown liquid
I2 - grey crysaline solid

Question 5

why does bromine for an orange gas

Answer 5

it is a volatile liquid

Question 6

what does iodine form when heated

Answer 6

purple vapour

Question 7

what colour is iodine dissolved in water (aq)

Answer 7

brown

Question 8

obseravtions for:
- SO2
- S
- H2S

Answer 8

SO2: colourless gass turns blue litmus paper red
S: pale yellow solid
H2S: colourless gas- rotten egg smell

Question 9

explain how cis platin functions as an anticancer drug

+ side effects and how to reduce side effects

Answer 9

PtCl2(NH3)2
Cisplatin works by binding to two different Guanine (G) base groups on a strand of DNA.
The cisplatin undergoes a ligand substitution reaction with each Guanine – the N atom on the guanine replaces the Cl
atom on the cisplatin and a dative covalent bond is formed with Pt.
DNA (helix) distorted; this prevents DNA replication
stops the cell dividing
Mainly affects cells that divide/replicate faster e.g. skin, hair, epithelial cells (causing hair loss, nausea etc)
To minimise effects – lower the dose, take other medication (e.g. antinausea), methods that deliver drug only to
tumour/cancerous cells

Question 10

why does pentylamine have a higher boiling point than proplyamine

Answer 10

higher Mr, more e-, stronger VDW forces

Question 11

how does the IE graph change when its for 2nd IE vs 1st IE

Answer 11

shifts up, much larger values and shifts one to the right

Question 12

why do we use electrospray ionisation for larger molecules?

Answer 12

prevents fragmentation of the molecule.

Question 13

define enthalpy change

Answer 13

The enthalpy change is the heat energy change in a chemical reaction at constant pressure.

Question 14

colorimetry (determining unknown conc method)

Answer 14

• Make up solutions of known
  concentration.
• Measure absorption or transmission
• Plot graph of absorbance vs
  concentration (calibration curve)
• Measure absorption of unknown and
  compare

• The amount of light absorbed is proportional to the concentration
  of the absorbing species.
• The colour of the filter is chosen to only allow the wavelengths of
  light through that would be most strongly absorbed by the
  coloured solution.
• Use a cuvette with distilled water to zero the colorimeter.

Question 15

conditions for reducing nitrile to amine

Answer 15

LiAlH3 (dry ether) and dilute acid (+4[H])
//
H2 (g) with Ni catalyst (+2H2)

Question 16

what can quarternary ammonium salts act as?

what do they help to do and give an example of what tehy are found in

Answer 16

cationic surfactants. (A cationic surfactant is a molecule that has a positively charged (cationic) head group and a long non-polar hydrocarbon tail.)
non polar hydrocarbon tail can bind to non polar substances like fats
positive end / head can dissolve in water and also bind to -ve charges substances
used to reduce static tension - found in fabric conditioners

Question 17

are salts of amines (ie protanated amines) more soluble than amines themselves

Answer 17

yes because ionic bonding trumps h bonding

Question 18

Why is phenylamine more soluble in HCl than in water?

Answer 18

Phenylamine (an amine) is weakly basic — it can react with strong acids like HCl to form a phenylammonium salt (a positively charged ion).
The phenylammonium salt formed is ionic and much more soluble in water than neutral phenylamine.