Hg For the reaction 2C4Hio(g) + 13 o2(g) rightarrow 8CO_2(g) + 10H20(g) delta H

Question

Hg For the reaction 2C4Hio(g) + 13 o2(g) rightarrow 8CO_2(g) + 10H20(g) delta H degree is -125 kj/mol and delta S degree is +253 J/K . mol. This reaction is spontaneous only at high temperature spontaneous only at low temperature nonspontaneous at all temperatures spontaneous at all temperatures unable to determine without more information Consider the reaction: Ag+ (aq) + Cl^- (aq)RIGHTARROW AgCl (s) Given the following table of thermodynamic data, Determine the temperature (in degree C) above which the reaction is nonspontaneous under standard conditions. 150 432 1230 1640 133

Explanation / Answer

17) delta G0 = delta H0 - T*delta S0 = -125000 - 298*253 = -200394 J = -200.394 kJ/mole

Since delta G0 < 0 ; hence the reaction is spontaneous

but as delta H0 is < 0 ; i.e the reaction is exothermic and hence increase in temperature decreases the numerical value of it

Thus, the correct option is :-(B)

18) Ag+(aq) + Cl-(aq) --------> AgCl(s)

delta H0rkn = delta H0f AgCl(s) - (delta H0f Ag+(aq) + delta H0f Cl-(aq)) = -65.7 kJ/mole

delta S0rkn = delta S0f AgCl(s) - (delta S0f Ag+(aq) + delta S0f Cl-(aq)) = -34.32 J

Now, delta G0 = delta H0 - T*delta S0

Also, for the reaction to be non-spontaneous, delta G0 > 0

Thus, delta H0 - T*delta S0 > 0

or, -65700 - T*(-34.32) > 0

or, T > 1914.33 K

or, T > 1641 K

hence the correct option is :- (D)

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