3. IIse the following tahle and rsn to ancwer the questions Standard Heat of Sub

Question

3. IIse the following tahle and rsn to ancwer the questions Standard Heat of Substance in kf mol C(s) C0:(8) H:(g) H20(0) 0:(8) 5.69 213.6 130.6 69.96 205.0 2263 393.5 285.85 0.00 The enthalpy change for the combustios of betyrie acid at 25 *C, AFf comb- is -2,183.5 kilojoules per mole 25 "C. a) From the data above, calculate the standsed heat of formation, l, for butyric acid at b) Write a correctly balanced equation for the formation of butyric acid from its elements e) Calculate the standard entropy change, AS, for the formation of butyric acid a 25 "C. The entropy change. A, for he combustion reaction above is-1171 J K1 at 25 °C d) Calculate the standard free energy of formation, ·for butync acid at 25 "C 4. Use the following formation rxn to answer the questions

Explanation / Answer

The combustion of butyric acid is

C3H7COOH(l)+ 5O2(g)----à4CO2(g)+ 4H2O(l)

Standard heat of reaction = sum of standard heat of reaction of products- sum of standard heat of reaction of reactants

=4* standard heat of formation of CO2(g)+ 4* standard heat of formation of H2O(l)- {1* Standard heat of formation of C3H7COOH+ 5* standard heat of formation of O2}=-2183.5

Where ,4,4,1 and 5 are coefficients of CO2, H2O, C3H7COOH and O2 repectively.

4*(-393.5)+4*(-285.85)- {1*(standard heat of formation of butyric acid)= -2183.5

Standard heat of formation of butyric acid = 4*(-393.5)+ 4*(-285.85)+2183.5 =-532.5 Kj/mole

2. formation of butyric acid from its elements is 4C(s) + 4H2(g) + O2(g) ---->C3H7COOH(l)

3.

The combustion of butyric acid is

C3H7COOH(l)+ 5O2(g)----à4CO2(g)+ 4H2O(l)

Standard entropy of reaction = sum of standard entropy of products- sum of standard entropy of reactants

=4* standard heat of formation of CO2(g)+ 4* standard heat of formation of H2O(l)- {1* Standard entropy of formation of C3H7COOH+ 5* standard entropy of formation of O2}=-2183.5

Where ,4,4,1 and 5 are coefficients of CO2, H2O, C3H7COOH and O2 repectively.

4*(213.6)+4*(69.96)- {1*(standard entropy of formation of butyric acid+5* 205} =-117.1

Standard entropy of formation of butyric acid+5*205 = 4*(213.6)+ 4*(69.96)+117.1

Standard entropy of formation iof butyric acid =226.34 J/K

3. deltaGf =deltaHo-T*deltaSo= -2183.5-298*(-117.1)/1000= -2148.6 Kj/mole

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