Using standard enthalpies of formation from Appendix 2A, calculate the standard

Question

Using standard enthalpies of formation from Appendix 2A, calculate the standard reaction enthalpy for each of the following reactions. the final stage in the production of nitric acid: 3 NO_2 (g) + H_2 O (l) rightarrow 2 HNO_3 (aq) + NO(g) the industrial synthesis of boron trifluoride: B_2 O_3 (s) + 3 CaF_2 (s) rightarrow 2 BF_3 (g) + 3 CaO (s) the formation of a sulfide by the action of hydrogen sulfide on an aqueous solution of a base: H_2 S(aq) + 2 KOH (aq) rightarrow K_2 S (aq) + 2 H_2 O (1)

Explanation / Answer

a)

Std. Enthalpy of Reaction

HRxn = Hproducts - Hreactants

HRxn = 2*HNO3 + NO - (3*NO2 + H2O)

HRxn = (2*(-174.1) + 91.3) - (3*33.2 + -285.8)

HRxn = -70.7 kJ

b)

B2O3 + 3CaF2 = 2BF3 + 3CaO

HRxn = 2*BF3 + 3CAO - (B2O3 + 3CaF2)

HRxn = (2* -1137.002 3*-634.9 ) - (1273.5 + 3*-1228.0) = -1768.204 kJ

c)

HRxn = K2S + 2H2O - (H2S + 2KOH)

HJRxn = (-363.1712 + 2*-285.8) - (-20.6 + 2*-425.84752)

HRxn = -62.47616 kJ

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