a) 40 (9) Use the Hess\'s law for the following processes: ak, =-802 kJ (i) CH4

Question

a) 40 (9) Use the Hess's law for the following processes: ak, =-802 kJ (i) CH4 (g) + 202 (g) CO2 (g) + 2 H2O (g) (ii) H2O (g) H2O (l) CH4 (g) + 2O2 (g) CO2 (g) + 2 H2O (l) (iii) (a) AK, =-846 kJ (c) AH3 -44 kJ What is the enthalpy change , for the reaction (iii)? (b) H,--890 kJ (d) AH3--802 kJ (10) For reaction: 2 HN3 (I) + 2NO (g) H2O2 (l) + 4 N2 (g), J. (a) -892 300 (c)-892300-2RT (b)-892 300+2RT (d)-892300-RT 2. Problems: constant 25C. Calculate (1) 10 mol H2 gas (perfect gas) is expanded from 2 L to 10 Lat w, q, AU, AH for each of the following processes: (a) isothermal reversible expansion. (b) at constant pressure Pex 1 atm (30 points)

Explanation / Answer

9) multiply eqn two with 2 and add to 1st u will get the main eqn

H3=H1+2*H2

=-802-88

=-890 J

10) H= U+nRT

n = 5-4

= 1

Therefore

U= -892300-RT J

2)

1)W= n*R*T* ln(V2/V1)

=n* R*T*ln(5)

=10* 8.314*298*ln(5)

=39874.98J

2)

W= P*V

= 1atm * 5 L

= 101325*5*10^-3

= 506.625J

2)

H(298) = 52.26-226.7

=-174.1kJ/mole

H450= v*cp*T+H298

v= stichometry cofficent of reactant, product

- ve for reactant ,+ve for product

H450=43.6*(450-298)-43.9*(450-298)-28.8*(450-298)+(-174.1)

=-4597.3 kJ/mole

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