IB CHEMISTRY

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Assessment Bank

Reactivity 1.2 Exam Practice

Section A: Multiple Choice

1. Which equation represents the Standard Enthalpy of Formation of Ethanol?

A. 2C(s)+3H2(g)+12O2(g)ā†’C2H5OH(l)2C(s) + 3H_2(g) + \frac{1}{2}O_2(g) \rightarrow C_2H_5OH(l) (Correct)
B. 2C(g)+6H(g)+O(g)ā†’C2H5OH(l)2C(g) + 6H(g) + O(g) \rightarrow C_2H_5OH(l)
C. C2H4(g)+H2O(g)ā†’C2H5OH(l)C_2H_4(g) + H_2O(g) \rightarrow C_2H_5OH(l)
D. 2CO2(g)+3H2O(l)ā†’C2H5OH(l)+3O2(g)2CO_2(g) + 3H_2O(l) \rightarrow C_2H_5OH(l) + 3O_2(g)

Section B: Structured Questions

Q1: Hess's Law Cycle [3 marks]

Calculate the enthalpy change for the reaction: Aā†’BA \rightarrow B

Given:

  • Aā†’CĪ”H=āˆ’100A \rightarrow C \quad \Delta H = -100
  • Bā†’CĪ”H=āˆ’40B \rightarrow C \quad \Delta H = -40

Examiner's Markscheme

1. Route: Aā†’Cā†’BA \rightarrow C \rightarrow B.

2. Reverse calculation: Ī”H=(āˆ’100)āˆ’(āˆ’40)\Delta H = (-100) - (-40).

3. Answer: -60 kJ/mol.