Textbook Question
Methanol (CH3OH) can be made by the controlled oxidation of methane: CH4(g) + 12 O2(g) → CH3OH(g) (b) Will ΔG for the reaction increase, decrease, or stay unchanged with increasing temperature?
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Ch.19 - Chemical Thermodynamics
Chapter 19, Problem 73
Acetylene gas, C2H2(g), is used in welding. (b) How much heat is produced in burning 1 mol of C2H2 under standard conditions if both reactants and products are brought to 298 K?
Verified step by step guidance1
Identify the chemical reaction for the combustion of acetylene: \( \text{C}_2\text{H}_2(g) + \frac{5}{2} \text{O}_2(g) \rightarrow 2 \text{CO}_2(g) + \text{H}_2\text{O}(l) \).
Determine the standard enthalpy change of the reaction (\( \Delta H^\circ_{\text{rxn}} \)) using standard enthalpies of formation: \( \Delta H^\circ_{\text{rxn}} = \sum \Delta H^\circ_f(\text{products}) - \sum \Delta H^\circ_f(\text{reactants}) \).
Look up the standard enthalpies of formation for each substance involved in the reaction: \( \Delta H^\circ_f(\text{C}_2\text{H}_2(g)) \), \( \Delta H^\circ_f(\text{O}_2(g)) \), \( \Delta H^\circ_f(\text{CO}_2(g)) \), and \( \Delta H^\circ_f(\text{H}_2\text{O}(l)) \).
Substitute the values into the enthalpy change equation: \( \Delta H^\circ_{\text{rxn}} = [2 \times \Delta H^\circ_f(\text{CO}_2(g)) + \Delta H^\circ_f(\text{H}_2\text{O}(l))] - [\Delta H^\circ_f(\text{C}_2\text{H}_2(g)) + \frac{5}{2} \times \Delta H^\circ_f(\text{O}_2(g))] \).
Calculate the \( \Delta H^\circ_{\text{rxn}} \) to find the heat produced when 1 mol of \( \text{C}_2\text{H}_2 \) is burned under standard conditions.
Related Practice
Open Question
(a) Use data in Appendix C to estimate the boiling point of benzene, C6H6. (b) Use a reference source, such as the CRC Handbook of Chemistry and Physics, to find the experimental boiling point of benzene.
Textbook Question
(a) Using data in Appendix C, estimate the temperature at which the free-energy change for the transformation from I2(s) to I2(g) is zero. (b) Use a reference source, such as Web Elements (www.webelements.com), to find the experimental melting and boiling points of I2. (c) Which of the values in part (b) is closer to the value you obtained in part (a)?
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Textbook Question
The fuel in high-efficiency natural-gas vehicles consists primarily of methane (CH4). (a) How much heat is produced in burning 1 mol of CH4(g) under standard conditions if reactants and products are brought to 298 K and H2O(l) is formed?
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Textbook Question
The fuel in high-efficiency natural-gas vehicles consists primarily of methane (CH4). (b) What is the maximum amount of useful work that can be accomplished under standard conditions by this system?
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Open Question
Indicate whether ΔG increases, decreases, or stays the same for each of the following reactions as the partial pressure of O2 is increased: (a) 2 CO(g) + O2(g) → 2 CO2(g) (b) 2 H2O2(l) → 2 H2O(l) + O2(g) (c) 2 KClO3(s) → 2 KCl(s) + 3 O2(g)