Question

The reaction of sodium metal with cold water is
A. Endothermic
B. Exothermic
C. Both a and b
D. Neither a nor b

Answer 1

Hint: As we know that the metal like sodium reacts with water rapidly as sodium is hygroscopic in nature. Sodium metal has the property of being hygroscopic by nature and it reacts readily with water.

Complete step by step answer:
As we know that there are two types of reactions one is endothermic and other is exothermic based upon the amount of energy released or amount of energy consumed to form or break the new bond in formation of new compounds from the reactants.
Endothermic reactions are the one which consume energy during the reaction and the new product is formed.
Exothermic reaction is the reaction in which the energy is released in the form of heat energy where the product form will convert the wall of the vessel hot in which the reaction is carried out.
The reaction of sodium metal with water results in the formation of sodium hydroxide \[\left( {NaOH} \right)\] and hydrogen gas\[\left( {{H_2}} \right)\]. The reaction with water is exothermic, heat will be released in the surrounding when the reaction is going on.

Hence, the correct option is (B).

Note:
During the reaction, the sodium metal becomes so hot that it catches fire and burns with a color of flame, it depends on the amount of heat released. More the heat, the more the substance becomes hot.