Question

The number of electron in 2 coulomb of charge is
$
  {\text{A}}{\text{. 5}} \times {\text{1}}{{\text{0}}^{29}} \\
  {\text{B}}{\text{. 12}}{\text{.5}} \times {\text{1}}{{\text{0}}^{18}} \\
  {\text{C}}{\text{. 1}}{\text{.6}} \times {\text{1}}{{\text{0}}^{19}} \\
  {\text{D}}{\text{. 9}} \times {\text{1}}{{\text{0}}^{11}} \\
$

Answer 1

Hint: The charge on an electron is a basic unit of charge which is equal to $1.6 \times {10^{ - 19}}C$. All charges other than electrons are multiples of this basic value of charge.

Complete step-by-step answer:
Charge is the property of matter by which virtue of which it exhibits attraction or repulsion towards other charges. Charge can either be positive or negative. Like charges repel each other and opposite charges attract each other.

The basic unit of charge is e = $1.6 \times {10^{ - 19}}C$ which is the charge on an electron and has negative polarity.

Using this value of charge of electron, we can calculate the number of electrons in 2 coulomb of charge in the following way.

$

  1.6 \times {10^{ - 19}}C = 1{\text{ }}electron \\
   \Rightarrow 1C = \dfrac{1}{{1.6 \times {{10}^{ - 19}}}}electrons \\
   \Rightarrow 1C = 0.625 \times {10^{19}}electrons \\
   \Rightarrow 2C = 2 \times 0.625 \times {10^{19}}electrons \\
   \Rightarrow 2C = 1.25 \times {10^{19}}electrons = 12.5 \times {10^{18}}electrons \\

$


This is the required number of electrons in 2 coulombs of charge. So, the correct answer is option B.

Additional Information:
An atom consists of a positively charged nucleus at the centre with electrons revolving around it in closed orbits. The nucleus contains nucleons which are neutrons and protons. Neutrons have zero charge while protons are positively charged with the same charge as an electron. The electrons have very small mass compared to nucleons while nucleons are responsible for giving mass to an atom so all the mass of the atom is concentrated in the nucleus. The electrons are responsible for all the chemical properties of a substance while nucleons are responsible for nuclear properties like radioactivity, etc.

Note: The minimum amount of charge possible is e = $1.6 \times {10^{ - 19}}C$ which is the charge on an electron. The charge is quantized which means that it occurs in the units of e. Fractional charges do not exist in nature.