【正确答案】From the sign of，the forward reaction gives off heat. Therefore the equlibrium formation of is favored by as low a temperature as practicable. In a reaction like this，the choice of temperature requies a compromise between equilibrium considerations and rate considerations. The lower the temperature，the higher the equilibrium yield of NH3． On the other hand，the rate at which the system will reach equilibrium is lower in the lower temperature. The forward reaction is accompanied by a decreased molecules in mot， therafore increased pressure will give a larger proportion of in the equilibrium mixture. A catalyst should be employed to speed up the approach to equilibrium.