To determine if a chemical equation is correct, you need to check if the law of conservation of mass is obeyed. This means that the total mass of the reactants (substances on the left side of the equation) should be equal to the total mass of the products (substances on the right side of the equation).

Consider the following reaction as an example:

2H2 + O2 → 2H2O

In this equation, 2 molecules of hydrogen gas (H2) react with 1 molecule of oxygen gas (O2) to produce 2 molecules of water (H2O). If we calculate the total mass of the reactants and products, we get:

Reactants: 2(2 g) + 1(32 g) = 36 g

Products: 2(18 g) = 36 g

As you can see, the total mass of the reactants is equal to the total mass of the products, so the law of conservation of mass is obeyed and the equation is correct.

However, it's important to note that a balanced chemical equation only ensures that the law of conservation of mass is followed, but it doesn't guarantee that the reaction will actually occur or that it will proceed under the specified conditions. Factors such as reaction rates, activation energy, and reaction conditions also play a role in determining whether a reaction will take place.