• # question_answer 52)   The spontaneity means, having the potential to proceed without the assistance of external agency. The processes which occur spontaneously are: (a) flow of heat from colder to warmer body (b) gas in a container contracting into one comer (c) gas expanding to fill the available volume (d) burning carbon in oxygen to give carbon dioxide

(c, d) Gas expands or diffuses in available space spontaneously, e.g., leakage of cooking gas gives smell of ethyl mercapton spontaneously. Moreover, burning of carbon to $C{{O}_{2}}$ is also spontaneous.