Zadanie 8

two points read from the line, for example (0.00310, −0.40) and (0.00340, −2.86), giving gradient $= \dfrac{-2.86 - (-0.40)}{0.00340 - 0.00310} = -8200\ \mathrm{K}$ ✔

«gradient = −E_a/R, so» E_a = 8200 × 8.31 = 6.81 × 10⁴ «J mol⁻¹» ✔

68.1 kJ mol⁻¹ «with the correct unit, kJ mol⁻¹ or J mol⁻¹» ✔

M1: the gradient from two points well separated on the line (accept -7900 to -8500); M2: E_a from the gradient and R (accept 65.6 to 70.6 kJ mol-1, or 65 600 to 70 600 J mol-1); M3: the unit, kJ mol-1 or J mol-1 consistent with the value. Award [2] for a correct final answer without the unit. Accept use of $\ln(k_1/k_2) = -\dfrac{E_a}{R}\left(\dfrac{1}{T_2} - \dfrac{1}{T_1}\right)$.