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± Enthalpy of Reaction: State and Stoichiometry Use the data below to answer the

ID: 909256 • Letter: #

Question

± Enthalpy of Reaction: State and Stoichiometry

Use the data below to answer the questions.

Keep in mind that the enthalpy of formation of an element in its standard state is zeroImagine a hypothetical process in which the methane molecule, CH4, is "expanded," by simultaneously extending all four CH bonds to infinity. We then have the process

CH4(g)C(g)+4H(g)

Part A

Compare the reaction for the "expansion" of methane with the reverse of the reaction that represents the standard enthalpy of formation. Which properties are the same for both reactions and which are different?

which items Same or Different

1.the enthalpy change of the reaction

2. the state of the carbon atoms

3. the number of atoms of each element

4. the state of the methane molecules

Substance Hf (kJ/mol) C(g) 718.4 CF4(g) 679.9 CH4(g) 74.8 H(g) 217.94 HF(g) 268.61

Explanation / Answer

(1) The enthalpy change of the reaction and (3) the number of atoms of each element properties are same for the both reactions, and (2) the state of the carbon atoms and (4) the state of the methane molecules.