4.09 Writing Thermochemical Equations Quiz

Which equation is a correctly written thermochemical equation? C3H8 (g) + 5O2 (g)→3CO2 (g) + 4H2O (l) , ΔH= −2,220 kJ/mol 2C8H18 + 25O2→16CO2 + 18H2O , ΔH= −5,471 kJ/mol Fe (s) + O2 (g)→Fe2O3 (s) , ΔH= −3,926 kJ NH4Cl→NH4 + + Cl−

C3H8 (g) + 5O2 (g)→3CO2 (g) + 4H2O (l) , ΔH= −2,220 kJ/mol

How does a phase change affect a thermochemical equation?

It can affect the ΔH value.

In which thermochemical equation would the ΔH be considered a heat of solution?

NH4Cl(s)→NH +4(aq)+Cl−(aq) , ΔH= +14.8 kJ/mol

Which enthalpy of reaction would the reaction represented by the diagram have? Diagram: https://static.k12.com/nextgen_media/assets/1085206-VHS_CHEM_S2_04_10_110_reactants_products_delta_H.jpg If Diagram doesn't work: The reactants have a higher temperature than the products, meaning heat was given off (exothermic).

ΔH<0

For the reaction, CH4 (g) + 2O2 (g)→CO2 (g) + 2H2O (l) , ΔH= −890 kJ , what will be the change in enthalpy when 3 moles of methane react in excess oxygen?

−2.67×10^3 kJ