In chemistry and physics, a valence electron is an outer shell electron that is associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed; in a single covalent bond, both atoms in the bond contribute one valence electron in order to form a shared pair.
The answer is 297.14 g/mol
<u>Answer:</u> The mass of sodium chloride solution present is 0.256 grams.
<u>Explanation:</u>
We are given:
39.0 % of sodium in sodium chloride solution
This means that 39.0 grams of sodium is present in 100 grams of sodium chloride solution
Mass of sodium given = 100 mg = 0.1 g (Conversion factor: 1 g = 1000 mg)
Applying unitary method:
If 39 grams of sodium metal is present in 100 grams of sodium chloride solution
So, if 0.1 grams of sodium metal will be present in = 
of sodium chloride solution.
Hence, the mass of sodium chloride solution present is 0.256 grams.
An oxygen gas is a diatomic molecule which means that each molecule is composed of 2 atoms. Its symbol is O2.
Each oxygen atom has a molar mass of 16 g/mol. The molar mass of oxygen gas is calculated below,
molar mass = 2 x (16 g/mol) = 32 g/mol
To determine the number of moles in 52.5 grams of oxygen, divide the given mass by the calculated molar mass.
n = 52.5 grams / (32 gram/ mol)
n = 1.64 moles
Thus, there are 1.64 moles of oxygen gas.
