2018 ppq Flashcards
State the aufbau principle.
Orbitals levels are filled in order of increasing energy.
Suggest how the hydroxyl groups allow pectin molecules to bind.
Hydrogen bonding
Describe the procedure for the accurate preparation of the 250cm3 solution from the weighed sample of hydrated sodium carbonate.
Dissolve/make a solution of the sodium carbonate in distilled/ deionised water (in a beaker).
Transfer the solution/it and the rinsings.
Use of a (250cm3) standard/ volumetric flask.
Make (the solution) up to the mark/line (in a standard/volumetric flask with distilled/deionised water)
State how transition metals can act as catalysts.
Incomplete subshells
Explain why but-1-ene has no geometric isomers.
But-1-ene has two hydrogens/the same group on first carbon of the C=C
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. (1)
Absorption of light (from the visible part of the spectrum) 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.
There is less conjugation
Larger gap/greater energy (absorbed).
Explain how ligands bond to metal ions to form complexes.
(Ligands) donate (lone/non-bonding) pairs of electrons (to the metal ion
Suggest why pure ethanol biofuel cannot be obtained from an ethanol/water mixture by distillation alone.
Boiling points are similar
State the feature that provides stability to aromatic rings.
Delocalised electrons
