Chem long answers

State and explain two improvements that could be made to increase the accuracy when calculating the enthalpy change of combustion of a fuel (4)

Instal draft screens to reduce heat loss

Lid on calorimeter to reduce heat loss

Move burner closer to beaker to improve heat transfer

Move thermometer off bottom of beaker more accurate change of temperature calculated

Stir to improve heat distribution

Use a copper calorimeter to improve heat transfer

What is the meaning of the term radical? Explain how chlorine radicals are formed in the stratosphere, naming the type of bond breaking that occurs (5)

Species with unpaired electron

Formed from R-Cl

By high energy

UV

Homolytic fission

It does show that phenol is acidic

Phenol not strong enough acid to react with carbonates

The students make some predictions About salicylic alcohol

They predict that salicylic alcohol with fizz with sodium carbonate solution

They also predict that salicylic alcohol will dehydrate when heated over al2o3 to give a substance that will decolourise bromine water

Comment on their predictions, giving chemical explanations (3)

(c) Both compound A and vinyl chloride have instantaneous dipole-induced dipole intermolecular bonds. Vinyl chloride also has permanent dipole-permanent dipole intermolecular bonds.

Explain how both these types of intermolecular bonds arise and predict, with a reason, which of compound A and vinyl chloride has the higher boiling point. (5)

(5)