This problem is asking for the percent by mass of hydrogen in hydrofluoric acid. At the end, the answer turns out to be D. 5% as shown below:
Percent compositions:
In chemistry, percent compositions are used for us to know the relative amount of a specific element in a compound. In order to do so for hydrogen, we use the following formula, which can also be applied to any other element in a given compound:
[tex]\% H=\frac{m_H*1}{M_{HF}}*100\%[/tex]
Where [tex]m_H[/tex] stands for the atomic mass of hydrogen and [tex]M_{HF}[/tex] for the molar mass of hydrofluoric acid. In such a way, we plug in the atomic masses of hydrogen (1.01 g/mol) and fluorine (19.0 g/mol) to obtain:
[tex]\% H=\frac{1.01g/mol*1}{1.01g/mol+19.0g/mol}*100\%\\\\\% H=5\%[/tex]
Learn more about percent compositions: https://brainly.com/question/12247957
