Question 17N.2.hl.TZ0.5
| Date | November 2017 | Marks available | [Maximum mark: 5] | Reference code | 17N.2.hl.TZ0.5 |
| Level | hl | Paper | 2 | Time zone | TZ0 |
| Command term | Calculate, Suggest | Question number | 5 | Adapted from | N/A |
Ethane-1,2-diol, HOCH2CH2OH, reacts with thionyl chloride, SOCl2, according to the reaction below.
HOCH2CH2OH (l) + 2SOCl2 (l) → ClCH2CH2Cl (l) + 2SO2 (g) + 2HCl (g)
Calculate the standard enthalpy change for this reaction using the following data.
[2]
ΔHθ = [–165.2 + 2(–296.9) + 2(–92.3)] – [–454.7 + 2(–245.7)]
«ΔHθ = +»2.5 «kJ»
Award [2] for correct final answer.
Award [1] for –2.5 «kJ».
Do not accept ECF for M2 if more than one error in M1.
Calculate the standard entropy change for this reaction using the following data.
[1]
«ΔSθ = [208.5 + 2(248.1) + 2(186.8)] – [166.9 + 2(278.6)]»
«ΔSθ = +» 354.2 «J K–1 mol–1»
The standard free energy change, ΔGθ, for the above reaction is –103 kJ mol–1 at 298 K.
Suggest why ΔGθ has a large negative value considering the sign of ΔHθ in part (a).
[2]
«3 moles of» liquid to «4 moles of» gas
OR
«large» positive ΔS
OR
«large» increase in entropy
TΔS > ΔH «at the reaction temperature»