Energy from a reaction was determined to be 3870 J using a water calorimeter, when burning 9.00 grams of H­2. What is the total enthalpy of the reaction?

860 J / mol

Explanation:

Enthalpy = Energy / no. of moles

no. of moles = mass / molar mass

Take the atomic mass of H = 1.0,

molar mass of H2 = 1.0 x 2

= 2.0

no. of moles of H2 = 9.00/2

= 4.5 mol

Hence,

Enthalpy = 3870 / 4.5

=860 J / mol

the correct answer would be d. hope this !