Some water is heated using the heat produced by the combustion of magnesium metal. Which values are needed to calculate the enthalpy change of reaction?

I.     The mass of magnesium

II.     The mass of the water

III.     The change in temperature of the water

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

D

There was some ambiguity in the wording of the question as to whether the enthalpy change required was that associated with the burning of the particular sample of magnesium, or the molar enthalpy change. For that reason it was decided to accept both response C and response D as correct.