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:
<h3>Percent compositions:</h3>
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:
Where 
stands for the atomic mass of hydrogen and 
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:
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Answer:
(a) Between methanol (CH₃OH) and glycerol (C₃H₅(OH)₃), the substance with the higher surface tension is glycerol (C₃H₅(OH)₃)
(b) Between tetrabromomethane (CBr₄) and chloroform (CHCl₃), the substance with the higher surface tension is chloroform (CHCl₃)
Explanation:
The surface tension of these substances at 20 °C given in mN/m, is as follows:
The surface tension of Methanol is 22.70
The surface tension of Tetrabromomethane is 26.95
The surface tension of Glycerol is 64.00
The surface tension of Chloroform is 27.50
(a) Between methanol (CH₃OH) and glycerol (C₃H₅(OH)₃), the substance with the higher surface tension is glycerol (C₃H₅(OH)₃)
(b) Between tetrabromomethane (CBr₄) and chloroform (CHCl₃), the substance with the higher surface tension is chloroform (CHCl₃)
It shows the type of atoms/elements in a substance
Different types of atoms have different emission spectrum - a concept supported by Bohr quantum theory - hence one is able to identify elements in a substance using a method called spectroscopy.
Explanation:
When an electron jumps from a low energy orbital to a higher energy orbital in an atom, it absorbs a specific wavelength of electromagnetic radiation (This is called absorption spectrum). Vice versa, if the same electron jumps from a higher to a lower energy orbital it releases the equivalent quantum energy in electromagnetic wave (This is called emission spectrum). Different types of atoms of different elements have a unique spectrum identifier.
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Learn more about spectroscopy;
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Answer:
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12, electrons dont have mass. only protons and neutrons do
