2018 Flashcards
after purification, the melting point should be
higher and over a narrower range
State the structural feature present that is responsible for the colour of these dye molecules.
Conjugated system
Explain fully how colour arises in these dye molecules.
- Electrons move from HOMO to LUMO.
- Absorption of light means that
light of the complementary colour is seen.
Explain fully why this dye molecule will absorb a shorter wavelength of light than the other two dye molecules.
- a smaller chromophore.
- Larger gap/greater energy
name reagent x used in step 3
lithium aluminium hydride
Suggest why pure ethanol biofuel cannot be obtained from an ethanol/water mixture by distillation alone.
Boiling points are similar
when is ethanolic potassium hydroxide used?
base induced elimination
State the feature that provides stability to aromatic rings.
delocalised electrons
Describe fully the procedure required to obtain results that
would allow a calibration graph to be drawn.
- Standard solutions are prepared
- A suitable filter used
- blank or solvent only
measurement. - Absorbance/transmittance of each solution is measured/plotted.
The second stage is to determine the concentration of a sample of the decamethylcobaltocene solution.
Describe how this would be carried out.
The absorbance/transmittance of the unknown is measured using the graph.
