It is of interest to establish the enthalpy of the reaction below at 1 atmospher
ID: 814692 • Letter: I
Question
It is of interest to establish the enthalpy of the reaction below at 1 atmosphere pressure.
a) Sketch a reaction scheme that would represent how the enthalpy could be calculated. Note you needto state all the data required for the calculation.
b) Using Hess' Law write an algebraic equation that would allow the calculation of the enthalpy of the reaction, referring to the standard reference temperature at 298K. You may need the information below
c) Using a driect application of Hess' Law calculate the enthalphy of the reaction at 1273K. Assume all phases are as expected from their transition temperatures.
d) What value to c) would you expect if you used Kirchoff's equation to evaluate the enthalphy. Justify your answer.
It is of interest to establish the enthalpy of the reaction below at 1 atmosphere pressure. a) Sketch a reaction scheme that would represent how the enthalpy could be calculated. Note you needto state all the data required for the calculation. b) Using Hess' Law write an algebraic equation that would allow the calculation of the enthalpy of the reaction, referring to the standard reference temperature at 298K. You may need the information below c) Using a driect application of Hess' Law calculate the enthalphy of the reaction at 1273K. Assume all phases are as expected from their transition temperatures. d) What value to c) would you expect if you used Kirchoff's equation to evaluate the enthalphy. Justify your answer.Explanation / Answer
a) ZnO(s) + C(s) -----> Zn(s) + CO(g) ----- (1)
Zn(s) at 298K ------> Zn(s) at 692K -------(2)
Zn(s) --------> Zn(l) ---------(3)
Zn(l) at 692K -------> Zn(l) at 1180K ------- (4)
Zn(l) -------> Zn(g) ------- (5)
Zn(g) at 1180K -------> Zn(g) at T --------(6)
Adding these yields the reaction in the problem.
b) deltaH = deltaH of (1) through (6)
c)deltaH at 1273K: Cp(Zn,s) = 25.47 J/mol-K
Cp(Zn,s)(692-298) + L(Zn, s-l) + Cp(Zn,l)(1180-692) + L(Zn,l-g) + Cp(Zn,g)(1273-1180) = 10035.18 + 7360 + 15860 + 114700 + 2027.4 = 149.98 kJ/mol
Kirchoff's law does not consider the phase transition and hence the expected deltaH is lower than that estimated by Hess's law.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.