Question

Balance the reaction for magnesium reacting with dioxygen to form magnesium oxide?

Answer 1

`Mg(s) + 1/2O_2(g) rarr MgO(s)`....

Explanation:

All chemical processes CONSERVE MASS and CONSERVE CHARGE. And representation of chemical reactions by means of equation musts reflect this so-called stoichiometry .

Here we used a half-integral coefficient....as I am perfectly free to do. That is `1/2O_2` represents a `16*g` mass of dioxygen gas, the which reacts with a `24.3*g` mass of magnesium metal to give a `40.3*g` mass of oxide. Of course, we could double the entire thing....

`2Mg(s) + O_2(g) rarr 2MgO`....

In both instances, mass and charge are balanced, as they absolutely must be if we purport to represent chemical change. When we use bimolecules such as `O_2`, and `N_2`, often a `1/2` coefficient can be useful. For instance...

`C_2H_6(g) + 7/2O_2(g) rarr 2CO_2(g) +3H_2O(l)`

...or....

`3Li(s) + 1/2N_2(g) rarr Li_3N(s)`