# Is 2H_2(g) + O_2(g) rarr 2H_2O(l) the same as H_2(g) + 1/2O_2(g) rarr H_2O(l)?

Jun 5, 2017

Why not?

#### Explanation:

$2 {H}_{2} \left(g\right) + {O}_{2} \left(g\right) \rightarrow 2 {H}_{2} O \left(l\right)$

$36 \cdot g$ of reactants, and $36 \cdot g$ of products..........

VERSUS.......

${H}_{2} \left(g\right) + \frac{1}{2} {O}_{2} \left(g\right) \rightarrow {H}_{2} O \left(l\right)$

$18 \cdot g$ of reactants, and $18 \cdot g$ of products..........

Is mass conserved in each reaction? Well, clearly mass IS conserved. And while of course I cannot have half a molecule of dioxygen gas, I can certainly have a $16 \cdot g$ quantity of ${O}_{2} \left(g\right)$, i.e. a HALF A MOLE quantity of dioxygen gas. The use of such fractional coefficients often makes the arithmetic involved in stoichiometry a bit easier, which of course is why they are used.