Answer:
![2H_2O\rightarrow 2H_2+O_2](https://img.qammunity.org/2022/formulas/chemistry/high-school/tc3t0gedaag6cunwdxxdx3tq3esu222xfg.png)
Step-by-step explanation:
Hello there!
In this case, for the reaction by which water is decomposed to molecular hydrogen and oxygen:
![H_2O\rightarrow H_2+O_2](https://img.qammunity.org/2022/formulas/chemistry/high-school/jkymi978z1tcymd8j8qfpw12pai3h2ruh2.png)
It is necessary to perform the inspection balance process since there is a dissimilar number of atoms of oxygen on both sides; therefore, by putting a 2 on water we balance oxygen:
![2H_2O\rightarrow H_2+O_2](https://img.qammunity.org/2022/formulas/chemistry/high-school/23ifwks9xxep36br5yfm9crmnxlnqnwif2.png)
But now, there are four hydrogens on the left; therefore, we put a 2 on hydrogen to finally balance it:
![2H_2O\rightarrow 2H_2+O_2](https://img.qammunity.org/2022/formulas/chemistry/high-school/tc3t0gedaag6cunwdxxdx3tq3esu222xfg.png)
And obviously, the coefficient in oxygen is an unwritten 1.
Best regards!