91Ó°ÊÓ

Which of the enthalpies of combustion in Table 5.2 the table are also standard enthalpies of formation?

How many kilojoules of heat will be released when exactly 1 mole of manganese, Mn, is burned to form Mn₃O₄(s) at standard state conditions?

How many kilojoules of heat will be released when exactly 1 mole of iron, Fe, is burned to form Fe₂O₃(s) at standard state conditions?

The following sequence of reactions occurs in the commercial production of aqueous nitric acid:

4NH₃(g) + 5O₂(g)⟶4NO(g) + 6H₂O(l) ΔH= −907 kJ

2NO(g) + O₂(²µ)⟶2±·°¿₂(g) ΔH= −113 kJ

3NO₂ + H₂°¿(±ô)⟶2±á±·°¿₃(aq) + NO(g) ΔH= −139 kJ

Determine the total energy change for the production of one mole of aqueous nitric acid by this process.

Using the data in Appendix G, calculate the standard enthalpy change for each of the following reactions:

(a) N₂(g) + O₂(²µ)⟶2±·°¿(g)

(b) Si(s) + 2Cl₂(²µ)⟶S¾±°ä±ô₄(g)

(c) Fe₂O₃(s) + 3H₂(g)⟶2Fe(s) + 3H₂O(l)

(d) 2LiOH(s) + CO₂(²µ)⟶L¾±₂CO₃(s) + H₂O(g)

Using the data in Appendix G, calculate the standard enthalpy change for each of the following reactions:

(a) Si(s) + 2F₂(²µ)⟶S¾±¹ó₄(g)

(b) 2C(s) + 2H₂(g) + O₂(²µ)⟶C±á₃CO₂H(l)

(c) CH₄(g) + N₂(g)⟶HCN(g) + NH₃(g)

(d) CS₂(g) + 3Cl₂(²µ)⟶C°ä±ô₄(g) + S₂Cl₂(g)

Calculate the enthalpy of combustion of propane, C₃H₈(g), for the formation of H₂O(g) and CO₂(g). The enthalpy of formation of propane is -104 kJ/mol.

In the early days of automobiles, illumination at night was provided by burning acetylene, C₂H₂. Though no longer used as auto headlamps, acetylene is still used as a source of light by some cave explorers. The acetylene is (was) prepared in the lamp by the reaction of water with calcium carbide, CaC₂:

\({\bf{Ca}}{{\bf{C}}_{\bf{2}}}\left( {\bf{s}} \right){\bf{ + 2}}{{\bf{H}}_{\bf{2}}}{\bf{O}}\left( {\bf{l}} \right) \to {\bf{Ca}}{\left( {{\bf{OH}}} \right)_{\bf{2}}}\left( {\bf{s}} \right){\bf{ + }}{{\bf{C}}_{\bf{2}}}{{\bf{H}}_{\bf{2}}}\left( {\bf{g}} \right)\)

Calculate the standard enthalpy of the reaction. The \({\bf{\Delta H}}_{\bf{f}}^{\bf{o}}\)of CaC₂is -15.14 kcal/mol.

From the data in Table 5.2, determine which of the following fuels produces the greatest amount of heat per gram when burned under standard conditions: CO(g), CH₄(g), or C₂H₂(g).

The enthalpy of combustion of hard coal averages -35 kJ/g, that of gasoline, \({\bf{1}}{\bf{.28 \times 1}}{{\bf{0}}^{\bf{5}}}\)kJ/gal. How many kilograms of hard coal provide the same amount of heat as is available from 1.0 gallons of gasoline? Assume that the density of gasoline is 0.692 g/mL (the same as the density of isooctane).