Question

The tailing of mercury on exposure to air shows a change in oxidation number by one. Is the given state true or false?

Answer 1

As we know that mercury tailing is basically the passing of ozone through mercury where it loses the meniscus and sticks to the glass due to the formation of mercury oxide. The chemical reaction involves two molecules of mercury and one molecule of ozone to form mercury oxide.

Complete step by step answer: As we already have learnt that when mercury reacts with ozone, it loses the meniscus and thus starts sticking to the glass walls of the thermometer because of the formation of mercury oxide and this is what we call mercury tailing. We know that two molecules of mercury react with one ozone molecule resulting in the formation of mercury oxide and oxygen. So, we can write the chemical reaction of this process as:
$2Hg + {O_3} \to H{g_2}O + {O_2}$
Now we know that when the element is present in its native state, its oxidation number is always zero. Thus we can say that mercury in its elemental form possess a zero oxidation state and the oxidation state of mercury in mercury oxide can be calculated by assuming the oxidation state as $x$ for mercury and we know that the oxidation state of oxygen is $- 2$, therefore on calculating for $x$ we will get:
$\Rightarrow 2x + ( - 2) = 0 \\\ \Rightarrow x = + 1 \\\$
Therefore, from the above explanation we can say that the given statement is true.

Note: Always remember that the meniscus which is lost during tailing can be restored by simply shaking it with water. Also, the oxidation number of a free element in its original form is taken as zero otherwise the oxidation number of any element is equal to the charge present on the ions.