Sulfuric acid (H_2SO_4), the most widely produced chemical in the world, is made

Question

Sulfuric acid (H_2SO_4), the most widely produced chemical in the world, is made by a two-step oxidation of sulfur to sulfur trioxide, SO_3, followed by reaction with water. Calculate Delta H degree_f, for SO_3 in kJ/mol, given the following data: S(s) + O_2(g) rightarrow SO_2 (g) Delta H degree = -296.8 kJ SO_2 (g) + 1/2 O_2 (g) righarrow SO_3(g) Delta H degree = -98 9 kJ The standard enthalpy change for the reaction of SO_3(g) with H_2O(l) to yield H_2SO_4(aq) is Delta H degree = -227.8 kJ. Use the information above to calculate Delta H degree_f, for H_2SO_4(aq) in kJ/mol. [for H_2O(l), Delta H degree_f = -285.8 kJ/mol.] Acetic acid (CH_3CO_2H), whose aqueous solutions are known as vinegar, is prepared by reaction of ethyl alcohol (CH_3CH_2OH) with oxygen: CH_3CH_2OH(l) + O_2(g) rightarrow CH_3CO_2H(l) + H_2O(l) Use the following data to calculate Delta H degree in kilojoules for the reaction: Delta H degree_f [CH_3CH_2OH(l)] = -277.7 kJ/mol Delta H degree_f [CH_2CO_2H(l)] = -484.5 kJ/mol Delta H degree_f [H_2O(l)] = -285.5 kJ/mol

Explanation / Answer

SO2(g)+1/2O2 (g) -à SO3(g)   delH0= -98.9 Kj     (2)

Addition of 1 and 2 gives S (s)+ 1.5O2(g)-à SO3(g) delH0= -395.7 Kj/mol

2.Standard enthalpy change= enthalpy change of products- enthalpy change of reactants= -227.8

x-(-395.7-285.8)= -227.8

x = -909.3 Kj/mol

3. Enthalpy change = enthalpy of products- enthalpy of reactants=

1*(-484.5)+1*(-285.8)+277.7-0= -484.5 Kj

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