Question

Complete and balance the following reaction:

$$\begin{gathered} \mathrm{Cu}+{\mathrm{O}}_2\stackrel{}{\to }\mathrm{\_\_\_\_\_\_} \\ \left(\mathrm{black}\right) \end{gathered}$$

Answer 1

Balanced chemical equation:

• A chemical equation in which the number of atoms of each element on both sides of the equation is equal is called a balanced chemical equation.

Step 1: Representation of the chemical reaction:

• When copper ($\mathrm{Cu}$) reacts with oxygen($\mathrm{O}$),it forms black copper oxide($\mathrm{CuO}$)
• $\underset{\mathrm{copper}}{2\mathrm{Cu}\left(\mathrm{s}\right)}+\underset{\mathrm{oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\stackrel{}{\to }\underset{\mathrm{copper}\mathrm{oxide}}{2\mathrm{CuO}\left(\mathrm{s}\right)}$

Step 2: Write the name and number of each element on both sides:

Element	No. of atoms on reactant side	No. of atoms on product side
Copper$\left(\mathrm{Cu}\right)$	1	1
Oxygen$\left(\mathrm{O}\right)$	2	1

Step 3: Balance the atom which is maximum in number:

• As the oxygen atoms are maximum in number i.e 2 on the reactant side.
• To balance the oxygen atom, oxygen needs to be multiplied by “2” on the product side
• On balancing oxygen on both sides, no of copper atoms becomes 2 on the product side and “1” on the reactant side.

Element	No. of atoms on reactant side	No. of atoms on product side
Copper$\left(\mathrm{Cu}\right)$	1	2
Oxygen$\left(\mathrm{O}\right)$	2	2

• To balance the copper atoms, one must be multiplied by 2 on the reactant side.
• Now the no of atoms of each element are equal on both side, hence it is the balanced chemical equation

Step 4: To check the correctness of the balanced equation, we count atoms of each element on both sides of the equation

Element	No. of atoms on the reactant side	No. of atoms on product side
Copper$\left(\mathrm{Cu}\right)$	2	2
Oxygen$\left(\mathrm{O}\right)$	2	2

Now, the equation is balanced.

Thus, the above reaction is the balanced chemical equation.