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Thermodynamics

# For the reaction $N_2(g) + 3H_2(g)\rightarrow 2NH_3(g) \Delta H = -95.4 \: kJ\: and\: \Delta S = -198.3\: J/K$  Calculate the temperature at which free energy change is equal to zero.

$\begin {array} {1 1} (A)\;-481\: K & \quad (B)\;207.8\: K \\ (C)\;481\: K & \quad (D)\;-207.8\: K \end {array}$

$\Delta G = \Delta H - T \Delta S$
Given, $\Delta G = 0$
So, $\Delta H - T \Delta S = 0 \: or,\: \Delta H = T \Delta S$
$T = \large\frac{ \Delta H}{ \Delta S}$$=\large\frac{ -95.4 \times 1000}{-198.3}$$ = 481 \: K$
Ans : (C)