Thermochemistry, calculating T given Q I have the reaction $\ce{2COCl2(g) -&gt; CCl4(l) + CO2(g)}$

And I want to calculate $T$ (temperature) when $Q = 10^{-4}$ at equilibrium. 

I tried simply putting $$T = -\frac{\Delta G^{0}}{\Delta S^{0}-R \ln Q}$$

Anyway, since $\Delta G^{0}$ for the reaction ($\pu{42000J/mol}$) is the value at standard condition (25 degrees celsius) I use that $\Delta G = \Delta H^{0} - T\times\Delta S^{0} + RT\ln Q$ where $\Delta G = 0$ since we're at equilibrium.

From this I obtain that $$T = \frac{\Delta H^{0}}{\Delta S^{0}-R\ln Q}$$

But which $\Delta H^{0}$ and $\Delta S^{0}$ values do I use here? I can calculate them from the standard conditions at 25 degrees celsius using SI, but that wouldnt be correct, would it? I'm rather confused by this task, which seems simple at first sight. Hope someone can clarify.

(The answer should be $\pu{476K}$)
We know that, at temperature T, $$\Delta G^0(T)=\Delta H^0(T)-T\Delta S^0(T)$$
From Hess's Law, we also know that 
$$\Delta H^0(T)=\Delta H^0(298)+???$$
and
$$\Delta S^0(T)=\Delta S^0(298)+???$$

That should be a good enough hint.