Chemistry · Oct / Nov 2023 · Paper 42 · Question 5

enthalpy change (of reaction)

M1 rate of reaction increases (1)

M2 more (CCl4) particles per unit volume (1)

M3 frequency of collisions between (CCl4 and H2O) particles increases (1)

M1 (position of) equilibrium moves to left hand side (1)

M2 more (gaseous) moles / molecules on right hand side (1)

M1 Labels mark

CCl4(g) + 2H2O(g) on reactant line

AND

CO2(g) + 4HCl(g) on product line

M2 Activation E mark

upward arrow labelled Ea from energy level of reactants to top of ‘hump’

M3 Energy change mark

one downward arrow labelled ΔH

AND

energy change starting from E level of reactants and finishing at E level of products

M1 minimum energy (1)

M2 that colliding particles must have to react (1)

(decreased by adding) catalyst

energy needed to break bonds in reactants

M1 [(4 × 340) + (4 × 460) = 3200 (kJ / mol) (1)

energy released when bond in carbon dioxide form

M2 2 × 805 = 1610 (kJ / mol) (1)

calculate H–Cl bond energy

M3 3200 – (1610 + E(4H–Cl)) = – 130

E(4H–Cl) = 3330 – 1610 = 1720 (kJ / mol) (1)

M4 1720 / 4 = 430 (kJ / mol) (1)