This is an **oxidation-reduction** (redox) reaction:

** N**V + *8* **e**- → **N**-III *(reduction)*

* 4* **O**-II - *8* **e**- → *4* **O**0 *(oxidation)*

### Word equation

* nitric acid + water → ammonia + oxygen*

### Input interpretation

* HNO3 + H2O → NH3 + O2*

* Nitric acid water ammonia oxygen*

### Balanced equation

Balance the chemical equation algebraically:

* HNO3 + H2O → NH3 + O2*

Add stoichiometric coefficients, ** c1,** to the reactants and products:

* c1 HNO3 + c2H2O → c3 NH3 + c4O2*

Set the number of atoms in the reactants equal to the number of atoms in the products for ** H, N **and

*O:**H: c1 + 2c2 = 3c3*

*N: c1 = c3*

*O: 3c1+ c2 = 2c4*

Since the coefficients are relative quantities and underdetermined, choose a coefficient to set arbitrarily. To keep the coefficients small, the arbitrary value is ordinarily one. For instance, set** c1 = 1** and solve the system of equations for the remaining coefficients:

*c1=1*

*c2=1*

*c3 = 1 *

*c4=2*

Substitute the coefficients into the chemical reaction to obtain the balanced equation:

**Answer**:

* HNO3 + H2O → NH3 + O2*