Thermochemistry: Standard Heats of Formation Worksheet
1.  Calculate Ho in kilojoules for the following reactions.

a) 2 NO(g) + O2(g) ---> 2 NO2(g) 

b) NaOH(s) + HCl(g) ----> NaCl(s) + H2O(g) 
2.  Use a standard enthalpies of formation table to determine the change in enthalpy for each of these reactions. 

a) 2 CO(g) + O2(g) ---> 2 CO2(g) 

b) CH4(g) + 2 O2(g) ---> CO2(g) + 2 H2O(l) 

c) 2 H2S(g) + 3 O2(g) ---> 2 H2O(l) + 2 SO2(g) 
3.  Calculate Ho for these reactions. In each case, state whether the reaction is exothermic or endothermic, rewrite the equation as a thermochemical equation to include the heat term, and indicate whether the products have a greater or smaller enthalpy than the reactants. Hfo of NH4Cl = 314.4 kJ/mol. 

a) SO2(g) + ½ O2(g) ---> SO3(g)

b) CaO(s) + H2O(l) ---> Ca(OH)2(s)

c) N2(g) + 3 H2(g) ---> 2 NH3(g)

d) C6H6(l) + 1½ O2(g) ---> 6 C(s) + 3 H2O(l) 

e) NH3(g) + HCl(g) ---> NH4Cl(s) 

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