$2\text{O}_3\text{(g)} \rightleftharpoons 3\text{O}_2\text{(g)}$
At $300\text{ K}$, ozone is fifty percent dissociated. The standard free energy change at this temperature and $1\text{ atm}$ pressure is $(-)\ \underline{\quad\quad\quad\quad}\ \text{J mol}^{-1}$. (Nearest integer)
$\left[\text{Given : } \ln 1.35 = 0.3 \text{ and } R = 8.3\text{ J K}^{-1}\text{ mol}^{-1}\right]$
