(i) measure the change in pressure per unit time at constant volume «2 mol of gas become 3 mol»

OR

measure the change in volume per unit time at constant pressure ✔

(ii) the molecules may collide with an unsuitable orientation ✔

the collision energy may be less than the activation energy ✔

(iii) rate $= k[\ce{Br2CO}][\ce{H2O}]$ ✔

(iv) water is the solvent, so $[\ce{H2O}]$ is very much larger than $[\ce{Br2CO}]$

(v) x-axis: $1/T$ «$\mathrm{K^{-1}}$» AND y-axis: $\ln k$ ✔

(vi) gradient «$= -\dfrac{E_\mathrm{a}}{R} = -\dfrac{15\,000}{8.31}$

(vii) second curve starting at the origin with a lower maximum displaced to higher energy, staying above the axis at high energy «area under both curves the same» ✔

(viii) $E_\mathrm{a}$ marked as a vertical line on the energy axis ✔

at the higher temperature a greater proportion of molecules have energy equal to or greater than $E_\mathrm{a}$ «larger area under the curve to the right of $E_\mathrm{a}$», so a greater fraction of collisions are successful ✔

(ix) the solid is chemically unchanged / its mass is unchanged at the end of the reaction ✔

the rate of reaction is greater in its presence «under otherwise identical conditions» ✔

(i) [1] a physical change that follows the increase in the amount of gas; do not accept pH measurement or titration. (ii) [2] M1 orientation; M2 energy below Ea. (iii) [1]. (iv) [1] excess water, concentration constant. (v) [1] both axes required; accept lg k on the y-axis. (vi) [1] accept −1.8 × 10^3 K; the negative sign is required. (vii) [1] no mark if the curve does not start at the origin, crosses the axis or has a larger area. (viii) [2] M1 Ea indicated; M2 greater proportion of molecules with E ≥ Ea. (ix) [2] M1 unchanged at the end; M2 rate increased. Answers that only quote the definition of a catalyst without an observation do not score.