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CHEM1101
• Use the standard heats of formation provided to calculate the molar heat of combustion of liquid methanol, CH3OH, in oxygen to produce CO2 and water. Your answer must include a balanced chemical equation for this reaction. Show all working. Marks 2 Data: Compound H2O(l) CH3OH(l) CO2(g) ΔfHº / kJ mol–1 –285.9 –238.6 –393.5
Answer:
CHEM1101 2012-N-12 November 2012
• Consider the process H2O(s) H2O(l) Give the sign of ΔH° at 273 K and explain your choice. Marks
Give the sign of ΔS° at 273 K and explain your choice.
How does ΔG° change with an increase in temperature? Explain your answer.
CHEM1101 2009-N-12 22/07(a)
• Pentane, CH3CH2CH2CH2CH3, burns completely in oxygen to form CO2(g) and H2O(g). Use the bond enthalpies given below to estimate the enthalpy change for this process. Marks 3 Bond Bond enthalpy (kJ mol–1) Bond Bond enthalpy (kJ mol–1) C–H 414 O–H 463 C–C 346 O–O 144 C=O 804 O=O 498
Answer: CHEM1101 2006-N-8 November 2006 • Glucose is a common food source. The net reaction for its metabolism in humans is: C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l) Calculate ΔH° for this reaction given the following heats of formation. ΔH°f (C6H12O6(s)) = –1274 kJ mol–1 ΔH°f (CO2(g)) = –393 kJ mol–1 ΔH°f (H2O(l)) = –285 kJ mol–1 Marks
Answer: If the combustion of glucose is carried out in air, water is produced as a vapour. Calculate ΔH° for the combustion of glucose in air given that H2O(l) → H2O(g) ΔH° = +44 kJ mol–1