Answer:
The correct answer is -
(a) spontaneous;
(b) nonspontaneous;
(c) spontaneous;
(d) nonspontaneous;
(e) spontaneous;
(f) spontaneous
Explanation:
(a) Liquid water freezing at a temperature below its freezing point.
in this reaction, there is no requirement of external energy or force to make it possible due to the fact that the temperature of the environment is less than the freezing point of water. So, the water will spontaneously freeze.
(b) Liquid water freezing at a temperature above its freezing point. the melting of ice takes place with the increase or absorbing the heat which is a nonspontaneous,
(c) The combustion of gasoline produces gas molecules, and release energy which means it is an exothermic reaction, the combustion of gasoline is a spontaneous reaction.
(d) A ball is thrown into the air is not a natural process and it requires force or energy to be complete and works against gravity, Therefore, it is a nonspontaneous reaction.
(e) A raindrop falling to the ground is a naturally occurring reaction without any external force and in the direction of gravity, thus it is a spontaneous reaction.
(f) Iron rusting in a moist atmosphere is a spontaneous reaction as it does not require energy to occur and it naturally takes place. It is a redox reaction.