【Daily Question】Theoretical Foundation 2019.5.31

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Multiple-choice question: Which of the following statements is correct? ( ) A. The standard molar enthalpy of formation of water is equal to the standard molar enthalpy of combustion of oxygen. B. The standard molar enthalpy of formation of water vapor is equal to the standard molar enthalpy of combustion of oxygen. C. The standard molar enthalpy of formation of water is equal to the standard molar enthalpy of combustion of hydrogen. D. The standard molar enthalpy of formation of water vapor is equal to the standard molar enthalpy of combustion of hydrogen. Answer: C. According to the definition of standard molar enthalpy of combustion, only (C) is correct. Since oxygen is a combustion accelerator, it does not have a standard molar enthalpy of combustion, and the combustion product of hydrogen is liquid water, rather than water vapor. Tip: The answer will be visible upon reply