Question

Which of the following metal/non-metal is stored in the water?
(A) Sodium
(B) Mercury
(C) Oxygen
(D) Phosphorous

Answer 1

Hint: Have a look at all the four metals given in the options. Find their positions in the periodic table and their atomic numbers. If an element is a store in water then, the element must be not reactive or inert to water. Think about the properties and reactions of these metals with water to get the answer.

Complete step by step solution:
-Let’s determine the properties of each element on reaction with water.
-Sodium is a metal which belongs to s-block in the periodic table. It is an alkali metal having atomic number 11. Sodium reacts explosively with water to form sodium hydroxide and release hydrogen gas.
$$2Na+2H_{2}O\to 2NaOH+H_2\uparrow$$
-So, sodium is stored in kerosene.
-Mercury is a metal which exists in the liquid state at room temperature. It belongs to d-block elements in the periodic table and has the atomic number, 80. Mercury does not react with water in the elemental state. Mercury vapour is a highly toxic element and therefore, it is handled with utmost caution. It is stored under vacuum.
-Oxygen is a non-metal which is a gas. It belongs to the p-block of the periodic table. It has the atomic number, 8. Atmospheric oxygen does get dissolved in water due to the aeration process happening in the ecosystem but oxygen is not stored in water.
-Phosphorus is a non-metal belonging to the p-block of the periodic table. It has the atomic number 15. Phosphorous doesn’t react with water, it is inert to water. White phosphorus reacts readily with oxygen present in the air and catches fire in the air to give dense white fumes.
$$P_4+5O_2\to P_4{O}_{10}$$
-Therefore, to break the contact of phosphorus and air, phosphorus is stored in water to prevent its oxidation.
-Therefore, the non-metal stored in water is Phosphorous.

The answer is option (D).

Note: Remember sodium is stored in kerosene because it explosively reacts with water. Mercury is stored in a vacuum because its vapours are highly toxic. Phosphorus is stored in water because it violently reacts with air. Oxygen is a gas present in the atmosphere and is stable. It can be stored under compressed or liquefied conditions in cylinders under pressure.