Ch.6 - Thermochemistry WorksheetSee all chapters
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Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
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Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: For ethanol, ΔvapH° = 43.5 kJ mol-1. (i) Calculate q, w, ΔH and ΔU when 1.75 mol C2H5OH (l) is vaporised at 260 K at constant external pressure. (ii) Explain whether the vaporisation of ethanol is exo

Problem

For ethanol, ΔvapH° = 43.5 kJ mol-1

(i) Calculate q, w, ΔH and ΔU when 1.75 mol C2H5OH (l) is vaporised at 260 K at constant external pressure. 

(ii) Explain whether the vaporisation of ethanol is exothermic or endothermic. 

(iii) If methanol has a ΔvapH° = 37.4 kJ mol-1, would you expect methanol or ethanol to have greater intermolecular forces? Give a reason for your answer.

Solution

We are given with the Heat of Vaporization of ethanol, ΔvapH° = 43.5 kJ mol-1 and asked several questions.


Part A. We are asked to calculate q, wΔH, and ΔU when 1.75 mol C2H5OH (l) is vaporized at 260 K at constant external pressure. 

Part B. We are asked to explain whether the vaporization of ethanol is exothermic or endothermic

Part C. We are asked to explain which between methanol and ethanol, from the ΔvapH° of both, would have greater intermolecular forces


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