Ammonia under a pressure of `15 atm`, at `27^(@)C` is heated to `327^(@)C` in a vessel in the pressure of catalyst. Under these conditions, `NH_(3)` partially decomposes to `H_(2)` and `N_(2)`. The vessel is such that the volume remains effectively constant, whereas the pressure increases to `50 atm`. Calculate the precentage of `NH_(3)` actually decomposed.