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Ch.6 - Thermochemistry
All textbooksTro 4th EditionCh.6 - ThermochemistryProblem 84
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Chapter 6, Problem 84

Write an equation for the formation of C2H4(g) from its elements in their standard states, and find ΔH°rxn for it in Appendix IIB.

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Identify the elements that make up \( \text{C}_2\text{H}_4(g) \), which are carbon (C) and hydrogen (H).
Determine the standard states of these elements: carbon is solid graphite \( \text{C(s)} \) and hydrogen is diatomic gas \( \text{H}_2(g) \).
Write the balanced chemical equation for the formation of \( \text{C}_2\text{H}_4(g) \) from its elements: \( 2\text{C(s)} + 2\text{H}_2(g) \rightarrow \text{C}_2\text{H}_4(g) \).
Look up the standard enthalpy of formation \( \Delta H_f^\circ \) for \( \text{C}_2\text{H}_4(g) \) in Appendix IIB.
Use the \( \Delta H_f^\circ \) value from the appendix to find \( \Delta H^\circ_{rxn} \) for the reaction, which is the same as \( \Delta H_f^\circ \) for \( \text{C}_2\text{H}_4(g) \) since it is formed from its elements in their standard states.
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Related Practice
Textbook Question

Calculate ΔHrxn for the reaction:

5 C(s) + 6 H2(g) → C5H12(l)

Use the following reactions and given ΔH's:

C5H12(l) + 8 O2(g) → 5 CO2(g) + 6 H2O(g) ΔH = –3244.8 kJ

C(s) + O2(g) → CO2(g) ΔH = –393.5 kJ

2 H2(g) + O2(g) → 2 H2O(g) ΔH = –483.5 kJ

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Textbook Question

Calculate ΔHrxn for the reaction:

CH4(g) + 4 Cl2(g) → CCl4(g) + 4 HCl(g)

Use the following reactions and given ΔH's:

C(s) + 2 H2(g) → CH4(g) ΔH = –74.6 kJ

C(s) + 2 Cl2(g) → CCl4( g) ΔH = –95.7 kJ

H2(g) + Cl2(g) → 2 HCl( g) ΔH = –92.3 kJ

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Textbook Question

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH °f for each in Appendix IIB. a. NH3(g)

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Textbook Question

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH°rxn for each in Appendix IIB. a. NO2(g)

Textbook Question

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH°rxn for each in Appendix IIB. b. MgCO3(s)

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Textbook Question

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH°rxn for each in Appendix IIB. d. CH3OH(l)

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