Skip to main content
Ch.6 - Thermochemistry
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Tro 4th EditionCh.6 - Thermochemistry문제 91
6장, 문제 91

Top fuel dragsters and funny cars burn nitromethane as fuel according to the balanced combustion equation: 2 CH3NO2(l) + 3/2O2(g) → 2 CO2(g) + 3 H2O(l) + N2(g) ΔH°rxn = –1418 kJ The enthalpy of combustion for nitromethane is –709.2 kJ/mol. Calculate the standard enthalpy of formation (ΔH°f ) for nitromethane.

검증된 단계별 안내
1
Identify the given information: the balanced combustion equation, the enthalpy change for the reaction (\( \Delta H^\circ_{rxn} = -1418 \text{ kJ} \)), and the enthalpy of combustion for nitromethane (\( -709.2 \text{ kJ/mol} \)).
Recognize that the enthalpy of combustion given is for one mole of nitromethane, while the balanced equation involves two moles. Therefore, the enthalpy change for the combustion of two moles of nitromethane is \( 2 \times (-709.2 \text{ kJ/mol}) \).
Use Hess's Law, which states that the total enthalpy change for a reaction is the same, no matter how many steps the reaction is carried out in. This allows us to relate the enthalpy of formation of reactants and products to the overall reaction enthalpy.
Write the expression for the enthalpy change of the reaction in terms of the enthalpies of formation: \( \Delta H^\circ_{rxn} = [2 \Delta H^\circ_f (\text{CO}_2) + 3 \Delta H^\circ_f (\text{H}_2\text{O}) + \Delta H^\circ_f (\text{N}_2)] - [2 \Delta H^\circ_f (\text{CH}_3\text{NO}_2) + \frac{3}{2} \Delta H^\circ_f (\text{O}_2)] \).
Solve for \( \Delta H^\circ_f (\text{CH}_3\text{NO}_2) \) using the known values: \( \Delta H^\circ_f (\text{CO}_2) = -393.5 \text{ kJ/mol} \), \( \Delta H^\circ_f (\text{H}_2\text{O}) = -285.8 \text{ kJ/mol} \), and \( \Delta H^\circ_f (\text{O}_2) = 0 \text{ kJ/mol} \) (since it is an element in its standard state).

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
영상 길이:
5m

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Enthalpy of Formation

The standard enthalpy of formation (ΔH°f) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. It is a crucial concept in thermodynamics, as it allows for the calculation of the energy changes associated with chemical reactions. The values of ΔH°f are typically tabulated and can be used to determine the enthalpy changes for reactions using Hess's law.
추천 영상:
가이드 코스
02:34
Enthalpy of Formation

Hess's Law

Hess's Law states that the total enthalpy change for a reaction is the same, regardless of the number of steps taken to achieve the reaction. This principle allows chemists to calculate the enthalpy change of a reaction by using known enthalpy changes of other reactions. In the context of the combustion of nitromethane, Hess's Law can be applied to relate the enthalpy of combustion to the enthalpy of formation.
추천 영상:
가이드 코스
02:03
Hess's Law

Combustion Reactions

Combustion reactions are exothermic reactions that occur when a substance reacts with oxygen, producing heat and light. In the case of nitromethane, the balanced combustion equation shows the reactants and products involved, allowing for the calculation of energy changes. Understanding the stoichiometry of combustion reactions is essential for determining the enthalpy changes associated with the formation and breakdown of fuels.
추천 영상:
가이드 코스
02:24
Combustion Apparatus
관련 실천
교과서 질문

Use standard enthalpies of formation to calculate ΔH°rxn for each reaction. d. N2O4(g) + 4 H2(g) → N2(g) + 4 H2O(g)

1
views
교과서 질문

Determine the mass of CO2 produced by burning enough of each fuel to produce 1.00×102 kJ of heat. a. CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g) ΔH°rxn = –802.3 kJ

3776
views
1
rank
교과서 질문

Ethanol (C2H5OH) can be made from the fermentation of crops and has been used as a fuel additive to gasoline. Write a balanced equation for the combustion of ethanol and calculate ΔH°rxn.

1712
views
교과서 질문

The explosive nitroglycerin (C3H5N3O9) decomposes rapidly upon ignition or sudden impact according to the balanced equation: 4 C3H5N3O9(l) → 12 CO2(g) + 10 H2O(g) + 6 N2(g) + O2(g) ΔH°rxn = –5678 kJ Calculate the standard enthalpy of formation (ΔH°f ) for nitroglycerin.

7072
views
교과서 질문

During photosynthesis, plants use energy from sunlight to form glucose (C6H12O6) and oxygen from carbon dioxide and water. Write a balanced equation for photosynthesis.

2183
views
교과서 질문

Methanol (CH3OH) has been suggested as a fuel to replace gasoline. Find ΔH°rxn, and determine the mass of carbon dioxide emitted per kJ of heat produced. Use the information from the previous exercise to calculate the same quantity for octane, C8H18. How does methanol compare to octane with respect to global warming?

1193
views