In the manufacture of ammonia by Haber's process

${\mathrm{N}}_{2\left(\mathrm{g}\right)}+3{\mathrm{H}}_2\rightleftharpoons 2{\mathrm{NH}}_{3\left(\mathrm{g}\right)}+92.3\mathrm{kJ}.$

which of the following conditions is unfavourable

The process of manufacturing of ammonia is an exothermic process,

On increasing temperature, the reaction will try to move in backward direction to neutralize its effect given by

 Lechatelier principle. Hence, increasing the temperature becomes unfavourable condition for manufacturing ammonia.