Question

If 1.0 gram of hydrogen reacts with 19.0 grams of fluorine, then what is the percent by mass of fluorine in the compound that is formed?

Answer 1

The reaction between hydrogen (H2) and fluorine (F2) is given below,
                                   H2 + F2 ---> 2HF
One mole of both hydrogen and fluorine yields to 2 moles of hydrogen fluoride. This can also be expressed as, 2 grams of hydrogen and 38 grams of fluorine will form 40 grams of hydrogen fluoride. From the given, only 20 grams of HF is formed with 19 g of it being fluorine. Thus, the percentage fluorine of the compound formed is 95%. 

Answer 2

Answer : The mass percent of fluorine in the compound is, 95%

Explanation :

Mass percent : It is defined as the mass of the given component present in the total mass of the compound.

Formula used :

$\text{Mass} \%\text{ F}=\frac{\text{Mass of F}}{\text{Mass of }H+\text{Mass of }F}\times 100$

Now put all the given values in this formula, we get the mass percent of fluorine in the compound.

$\text{Mass} \%\text{ F}=\frac{19g}{1g+19g}\times 100=95\%$

Therefore, the mass percent of fluorine in the compound is, 95%