Ch.6 - Thermochemistry WorksheetSee all chapters
All Chapters
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
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: Given the following thermochemical data:                                                                                ∆H°f (kJ)I. P4(s) + 6 Cl2(g) ⟶ 4 PCl3(g)                        –1225.6II. P4(s)

Problem

Given the following thermochemical data:

                                                                                ∆H°f (kJ)

I. P4(s) + 6 Cl2(g) ⟶ 4 PCl3(g)                        –1225.6

II. P4(s) + 5 O2(g) ⟶ P4O10(s)                         –2967.3

III. PCl3(g) + Cl2(g) ⟶ PCl5(g)                         –84.2

IV. PCl3(g) + 1/2 O2(g) ⟶ POCl3(g)                –285.7

Calculate the value of ∆H° for the following reaction:

P4O10(s) + 6 PCl5(g) ⟶ 10 POCl3(g)

A. –110.5 kJ 

B. –610.1 kJ 

C. –2682.2 kJ 

D. –4562.8 kJ

E. –7555.0 kJ

Solution

We’re being asked to determine the enthalpy change (ΔHrxn) for the chemical reaction:


P4O10(s) + 6 PCl5(g) ⟶ 10 POCl3(g)


We can use Hess’s Law to determine the enthalpy change of the overall reaction from the given reactions:

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