Question

What is the mass of $C{H_4}$ ?
A) $16g$
B) $26.6 \times {10^{22}}g$
C) $2.66 \times {10^{ - 23}}g$
D) $16{N_A}g$

Answer 1

Hint: We need to know that the molecular formula of methane is nothing but $C{H_4}$ . The molecular weight of the methane is equal to the sum of the atomic weight of the atom in methane. The Avogadro’s number is $6.023 \times {10^{ - 23}}$ . Avogadro is the first scientist to calculate the atomic weight of the atom. The Avogadro’s number is also represented by ${N_A}$ .

Formula used:
We can calculate the molecular weight of the substance by using the formula,
${\text{Molecular mass}} = \dfrac{{{\text{Molecular weight}}}}{{6.023 \times {{10}^{ - 23}}}}$

Complete step by step answer:
As we know that the IUPAC name of $C{H_4}$ is Methane. The one carbon atom and four hydrogen atoms in methane molecules.
The atomic weight of carbon is $12g$
The atomic weight of hydrogen is $1g$
Molecular weight = sum of the atomic weight of the atom in molecule.
The molecular weight of the methane is equal to the product of the atomic mass of the carbon and four times of the atomic mass of hydrogen.
The molecular weight of the methane = weight of carbon + $4x$weight of hydrogen
Molecular weight of methane $ = 12 + \left( {4 \times 1} \right)$
Molecular weight of methane $ = 16g$
The molecular weight of methane is $16g$ .
${\text{Molecular mass}} = \dfrac{{{\text{Molecular weight}}}}{{6.023 \times {{10}^{ - 23}}}}$
Molecular mass of the methane is equal to the atomic weight of the methane divided by Avogadro’s number.
Molecular mass $ = \dfrac{{16}}{{6.023\times{{10}^{ - 23}}}}$
Molecular mass $ = 2.66 \times {10^{23}}$
The mass of $C{H_4}$ is $2.66 \times {10^{23}}$.
So, the correct answer is “Option C”.

Note:
We have to remember that the mass and weight of the molecule is important for the study of molecules. The atomic weight of the atom is otherwise known as mass number. The mass number is nothing but the sum of the number of protons and neutrons in the atom. The charge of the proton is positive. The charge of a neutron is neutral. We need to know that the Avogadro’s number is also used to calculate the mole of the molecule.