Question

Balance the following chemical equations and identify the type of chemical reaction.

$\mathrm{HgO}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$

Answer 1

Step 1: Given equation

$\mathrm{HgO}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$

Step 2: Method used for balancing the equation

Using the traditional method of balancing chemical equations. According to the method:

First, compare the total number of atoms of each element on the reactant side and the product side.

Add stoichiometric coefficients to molecules containing an element that has a different number of atoms on the reactant side and the product side.

The coefficient must balance the number of atoms on each side.

Usually, the stoichiometric coefficients for hydrogen and oxygen atoms are assigned last.

The number of atoms of an element in one species must be obtained by multiplying the stoichiometric coefficient by the total number of atoms of that element present in 1 molecule of the species.

Repeat this process till the number of all the atoms of the reacting elements are equal on both the reactant and product sides.

Step 3: Balancing the given equation

The given equation is: $\mathrm{HgO}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$

Equation: $\mathrm{HgO}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$
Reactant Side	Product Side
1 Mercury atom	1 Mercury atom
1 Oxygen atom	2 Oxygen atoms

First, the oxygen atoms are balanced. After balancing the equation becomes: $2\mathrm{HgO}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$

Then the mercury atoms are balanced. After balancing the equation becomes: $2\mathrm{HgO}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }2\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$

The updated equation is: $2\mathrm{HgO}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }2\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$

Equation: $2\mathrm{HgO}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }2\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$
Reactant Side	Product Side
2 Mercury atoms	2 Mercury atoms
2 Oxygen atoms	2 Oxygen atoms

Since the number of all the atoms of the reacting elements are equal on both the reactant and product sides are equal, the equation is balanced.

Thermal Decomposition Reaction

Thermal decomposition is a chemical reaction that happens when a compound breaks down when heated.

In this reaction, mercury oxide is decomposed into mercury and oxygen on heating. Hence this reaction is a thermal decomposition reaction.

Hence the balanced equation is: $2\mathrm{HgO}\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }2\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$ and this reaction is a thermal decomposition reaction.