# If 1.0 g of hydrogen reacts completely with 19.0 g of fluorine, what is the percent by mass of hydrogen in the compound that is formed?

Feb 20, 2017

$\text{Well, 5%.......by mass......}$

#### Explanation:

With all the problems, a stoichiometric equation is the prerequisite:

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

As specified, you have stoichiometric equivalents of dihydrogen and difluorine. Why?

And so $\text{percentage by mass hydrogen}$

="Mass of hydrogen"/"Mass of hydrogen fluoride"xx100%

(1*g)/(20*g)xx100%=??%

And thus $20 \cdot g$ of hydrogen fluoride, which was the combined mass of the reactants, will result from stoichiometric reaction.