Question

A metal that exists as a liquid at room temperature is obtained by heating its sulphide in the presence of air. Identify the metal.
A. $Hg$
B. $I$
C. $Cl$
D. $Br$

Answer 1

Hint: The ores of metal which are less reactive can give the respective metals in pure form just by undergoing the process of heating. Sulphide of mercury is heated in presence of air so as to obtain mercuric oxide, which will give mercury metal by further heating.

Complete step by step answer:
Metals which are present at the low positions in reactivity series, can be easily extracted from their ore just by heating their sulphides or oxides.
If we consider the options given in the question, it is clear that iodine, bromine and chlorine are non-metals, in fact they are halogens. The question clearly mentioned that it should be a metal which exists in liquid form at room temperature. Since none of these fulfil this criteria, we will be solely focusing on the remaining option that is mercury.
Mercury is the only metal which tends to exist as liquid at room temperature. As you may have seen in the thermometers, the level of mercury is used to determine the temperature at which a substance is present. If we consider the question, the heating of mercuric sulphide can be represented by the following chemical equation.

\[2HgS+3{{O}_{2}}\xrightarrow{heat}2HgO+2S{{O}_{2}}\]

Here we can see two molecules of sulphide of mercury react with three molecules of oxygen gas in order to form mercuric oxide and sulphur dioxide. The form of mercury which exists in its sulphide form is called the ore of mercury. Now in the next step the mercuric oxide will give pure mercury and oxygen gas will be liberated in the process.

$2HgO\xrightarrow{heat}2Hg+{{O}_{2}}$

As we can see that the mercury oxide will give the mercury metal in further heating, and oxygen gas as a by-product. Since, mercury exists as liquid at room temperature and its sulphide ore can be heated in order to obtain pure form of mercury.

So, the correct answer is Option A.

Note: Mercury has a wide range of applications, due to its molten nature in standard conditions of temperature and pressure. It is used in labs for making barometers and thermometers, diffusion pumps, electrical apparatus like mercury switches etc. It is also used as electrodes in some specific types of electrolysis. It is also used for making cells, and batteries.