Question

#6-9

6. Calculate the enthalpy change for the reaction given below, using thermodynamic tables in your book (Appendix 2): CH(g)+02(B) HO(g) + CO,(g) (not balanced) 7. Calcium carbonate decomposes at high temperature to form carbon dioxide and calcium oxide: CaCO3 CO2+ CaO Using data from the textbook (Apendix 2), determine the heat of reaction. 8. When potassium chloride reacts with oxygen under the right conditions, potassium chlorate is formed: 2 KCI+3 02 2KCIO3 Using data from the textbook (Appendix 2), determine the heat of reaction.

Answer 1

Multiple questions, as per guideline first question should be answered ; maximum one to be answered.

6. oxidation of ethene :

C₂H₄(g) + 3 O₂ (g) -----------> 2 CO₂ (g) + 2 H₂O (g)    ∆_rH^o = ?

∆_rHº = _Products ΣHº_m − _Reactants ΣHº_m

∆_rHº= {2*Hº_m( CO₂ (g)) + 3*Hº_m(H₂O (g))} − {Hº_m( C₂H₄(g) ) + 3*Hº_m(O₂ (g) )}

Hº_m is the standard molar enthalpy of a species.

The standard enthalpies of formation of elements in their reference states are zero, thus

Hº_m( O₂ (g)) = 0

we have (from table ) :  Hº_m( C₂H₄(g) = 52.4 KJ /mol

  Hº_m( CO₂ (g) = -393.5 KJ /mol

  Hº_m(H₂O(g) )= −241.8 KJ /mol

putting values,

  ∆_rHº₂₉₈={2*-393.5 KJ /mol) + 2*−241.8 KJ /mol)} − {52.4 KJ /mol + 0 }

= -1323 KJ/mol

(-ve sign indicates exothermic reaction).