You will not measure the enthalpy of the reaction of in the coffee cup calorimeter because this reaction involves gases. Instead, you will use a well-known published value.

The reaction between H₂ and O₂ involves gaseous reactants, so it is not measured in the coffee cup calorimeter in this experiment. Instead, its published enthalpy value is used; therefore, the correct choice is H₂ and O₂.

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