Explanation:
<u>Moles is denoted by given mass divided by the molecular mass , </u>
Hence ,
n = w / m
n = moles ,
w = given mass ,
m = molecular mass .
For example ,
For a compound X ,
The given mass i.e. w = 20 g
and the molecular mass ,i.e. , m = 10 g / mol
Then the moles can easily be calculated by using the above formula ,
n = w / m
n = 20 g / 10 g/mol = 2 mol
Hence , answer = 2 mol.

<u>b. a positive cation and a negative anion</u>
✏ Anions are negative in nature while cations are positive in nature. Together they come together by an attractive electrostatic force to form an ionic bond.
ʰᵒᵖᵉ ⁱᵗ ʰᵉˡᵖˢ

A polar molecule is when the arrangement of the atoms in molecules are unequal where one end of the molecule has a positive charge while the other end has a negative charge. Examples of a polar molecule are water, ammonia, hydrogen sulfide and sulfur dioxide. The opposite is called a nonpolar molecule.