Process has enthalpy change= standard enthalpy of formation of CaF₂

Ca(s) + F₂(g) --> CaF₂(s)

Explain why the enthalpy of lattice dissociation for calcium fluoride is greater than that

for calcium chloride.

• Because fluoride (ion) smaller than chloride
• Electrostatic attraction stronger/ionic bonding stronger/attraction between ions stronger/more energy to separate ions

Use your knowledge of the equation ΔE = hν to suggest what happens to the e^-'s

in fluorite when ultra-violet light is absorbed and when visible light is given out.

• u.v. absorbed: electrons/they move to higher energy (levels)/ electrons excited

• visible light given out: electrons/they fall back down/move to lower energy levels

• Has ligand(s)
• linked by co-ordinate bonds

FUNCTION OF HAEMOGLOBIN IN THE BLOOD.

• Because it bonds to the iron/haemoglobin

• Displaces oxygen

Give one reason why methanol, synthesised from carbon dioxide and hydrogen, may

not be a carbon-neutral fuel.

CO2 /CO/CH4 may be produced during H2 manufacture/building the

plant/transport/operating the plant

• Hydrogen /H₂ gas/bubbles
• 1.0 mol dm^–3 HCl / H⁺
• At 298K and 100kPa
• Pt (electrode)

Suggest one reason why poisoning reduces the effectiveness of a heterogeneous

catalyst.

Suggest how poisoning of a catalyst, used in an industrial process, can be

minimised.

• Purify reactants
• Remove impurities

Give one reason, other than cost, why the platinum electrodes are made by coating a

porous ceramic material with platinum rather than by using platinum rods.

Suggest why the e.m.f. of a hydrogen– oxygen fuel cell, operating in acidic conditions,

is exactly the same as that of an alkaline fuel cell.

main advantage of a fuel cell over a

re-chargeable cell such as the nickel– cadmium cell when used to provide power for an

electric motor that propels a vehicle.

• Lack of pollution
• Hydrogen and oxygen supplied continuously
• Can be operated without stopping to recharge

• Ions can be regarded as point charges (or perfect spheres)
• Allow no polarisation
• Only bonding is ionic
• No covalent character