Q1/ The value of delta H rxn and delta S rxn for reaction 2NO(g)+O2(g)--->2NO2(g

Question

Q1/ The value of delta H rxn and delta S rxn for reaction   2NO(g)+O2(g)--->2NO2(g) are -12KJ and -146J/K. calculate delta G at 298K for this reaction. why do you think value of delta S is negative?

Q2/ Methanogenic bacteria convert acetic acid (CH3COOH) into  CO2(g) and CH4(g):

a) is the process endothermic or exothermic under standard condition?

b) is the reaction spontaneous under standard conditions?

c) calculate delta H and delta G in (KJ)?

delta H:                                         delta G:

CH3COOH  -484.5                       -389.9

CO2(g)     -393.5                             -394.4

CH4(g)   -74.8                                -50.8

Explanation / Answer

G=H - T*S=-12000 + 298*146=-31508J=-31.508Kj

s is (-)ve, beacause 3mole of gas reactant are producing 2mole gas(less).

delH=H(CO2)+H(H2O)-H(CH3COOH)=-393.5-74.8+484.5=17

delG=-394.4-50.8+389.9=-55.3

delH is (+)e....reaction is endothermic

delG is (-)ve....reaction is sponteneous

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