Question

Hydrofluoric acid contains what percent hydrogen by mass?
A.\[1.0\% \]
B.\[5.0\% \]
C.\[10\% \]
D.\[15\% \]
E.\[20\% \]

Answer 1

Hint: Hydrogen fluoride is a chemical compound that contains fluorine. It can exist as a dry gas or as a raging fluid, or it tends to be disintegrated in water. At the point when hydrogen fluoride is disintegrated in water, it could be called hydrofluoric acid. Hydrogen fluoride can be delivered when other fluoride-containing compounds, for example, ammonium fluoride are combined with water.

Complete step-by-step answer:Atoms of every element contain a specific number of protons. In fact, the quantity of protons figures out about the particle we are taking a look at (e.g., all iotas with six protons are carbon molecules); the number of protons in a particle is known as the nuclear number. Conversely, the number of neutrons for a given element can differ. Types of the very particle that contrast just in their number of neutrons are called isotopes. Together, the number of protons and the number of neutrons decide a component's mass number. In the event that you need to figure the number of neutrons a molecule has, you can essentially take away the number of protons, or nuclear number, from the mass number.
The atomic masses of hydrogen and fluorine are \[1g/mol\] and \[19g/mol\] respectively.
Mass percent of hydrogen in hydrofluoric acid \[(HF) = \dfrac{{atomic\,mass\,of \, hydrogen}}{{atomic\,mass\, of\,hydrogen \,+ atomic\,mass \, of\, fluorine}} \times 100\]
$\Rightarrow Mass\, percent\, of\, hydrogen\, in\, hydrofluoric\, acid [ = \dfrac{1}{{1 + 19}} \times 100 = 5\% $
Hence the correct option is B.

Note: A property closely identified with an atom's mass number is its nuclear mass. The nuclear mass of a solitary atom is basically its total mass and is regularly communicated in nuclear mass units or amu. By definition, a molecule of carbon with six neutrons, carbon-twelve, has a nuclear mass of twelve amu. However, an atom's nuclear mass will be exceptionally near its mass number yet will have some deviation in the decimal places.