Solid calcium reacts with dinitrogen and dioxygen to form solid calcium nitrate according to the unbalanced equation:
Ca(s)+N2(g)+O2(g)→Ca(NO3)2(s).
A thermodynamic database gives the following standard enthalpies of formation:
ΔHf∘[Ca(NO3)2(s)]=−940kJmol−1.
All elements in their standard states have ΔHf∘=0.
(a) Balance the chemical equation so that the coefficients are the smallest possible whole numbers.
(b) Using the coefficients from part (a), calculate the standard enthalpy change, in kJ, for the balanced reaction.
(c) Determine the standard enthalpy change, in kJ, per mole of Ca2+ produced in this reaction.
(d) A laboratory procedure uses 3.00g of calcium metal under standard conditions. Compute the heat absorbed or released, in kJ, when the reaction proceeds to completion, and state whether the process is exothermic or endothermic.