Question

The reaction of potassium and water is ……………. in nature.
A. endothermic
B. exothermic
C. electron donating
D. electron withdrawing

Answer 1

Hint: In order to solve this problem we need to know that when we react potassium with water then some amount of heat is released. So, we can determine the answer to this problem with this information.

Complete step-by-step answer:
In any of the reactions when the total amount of heat is released then the reaction is known to be exothermic.
The reaction of potassium and water is exothermic in nature.
Potassium reacts with water to form potassium ions, hydroxyl ions and releases hydrogen gas.
The reaction of the metal potassium with water can be written as:
$2K + 2{H_2}O \to 2{K^ + } + 2O{H^ - } + {H_2}$.
As it releases heat the reaction is exothermic from the definition of exothermic reactions above.
So, the correct option is B.

Note – When you get such problems to solve you just need to know the meaning of options given in the problem and the reaction which has been said. All these things can only be done if you have read such reactions and the concepts mentioned in the options. One can also remember that when we treat alkali metal or alkali earth metal with water it generally releases hydrogen gas and ionizes the metal ions. Knowing this you can solve various reactions related to metal and by balancing the reaction you will be getting the right reaction. We also need to know that when heat is evolved from the reaction then the reaction is exothermic and when the heat is involved in the reaction the reaction is endothermic. Knowing these things will help you further and will solve most of such problems.