Question

Calculate the molecular masses of $H_2$, $O_2$, $C{l}_2$, $C{O}_2$, $C{H}_4$, $C_2{H}_6$, $C_3{H}_6$, $N{H}_3$, $C{H}_{3}OH$

Answer 1

Hint: For calculating the molecular masses of the compounds, one should know the value of atomic masses of the atom from which the molecular weight can be calculated by adding the atomic mass of the atoms present in the molecule.

Complete step by step answer:
The molecular mass often referred to as molecular weight or molar mass is defined as the sum of the atomic weight of the atoms present in a molecule. The atomic weight of an atom is defined as the average mass of the atom measured in atomic mass units.
$H_2$
The atomic weight of hydrogen is 1.
The number of hydrogen atoms is 2.
The molecular weight of $H_2$is calculated as shown below.
$\Rightarrow molecularweight=2\times 1$
$\Rightarrow molecularweight=2$u
$O_2$
The atomic weight of oxygen is 16.
The number of oxygen atoms is 2.
The molecular weight of $O_2$is calculated as shown below.
$\Rightarrow molecularweight=2\times 16$
$\Rightarrow molecularweight=32$u
$C{l}_2$
The atomic weight of chlorine is 35.5.
The number of chlorine atoms is 2.
The molecular weight of $C{l}_2$is calculated as shown below.
$\Rightarrow molecularweight=2\times 35.5$
$\Rightarrow molecularweight=71$u
$C{O}_2$
The atomic weight of carbon is 12.
The atomic weight of oxygen is 16.
The number of carbon atoms is 1.
The number of oxygen atom is 2.
The molecular weight of $C{O}_2$is calculated as shown below.
$\Rightarrow molecularweight=12+2\times 16$
$\Rightarrow molecularweight=44$u
$C{H}_4$
The atomic weight of carbon is 12.
The atomic weight of hydrogen is 1
The number of carbon atoms is 1.
The number of hydrogen atoms is 4.
The molecular weight of $C{H}_4$is calculated as shown below.
$\Rightarrow molecularweight=12+4\times 1$
$\Rightarrow molecularweight=16$u
$C_2{H}_6$
The atomic weight of carbon is 12.
The atomic weight of hydrogen is 1
The number of carbon atoms is 2.
The number of hydrogen atoms is 6.
The molecular weight of $C_2{H}_6$is calculated as shown below.
$\Rightarrow molecularweight=2\times 12+6\times 1$
$\Rightarrow molecularweight=30$u
$C_3{H}_6$
The atomic weight of carbon is 12.
The atomic weight of hydrogen is 1
The number of carbon atoms is 3.
The number of hydrogen atoms is 6.
The molecular weight of $C_3{H}_6$is calculated as shown below.
$\Rightarrow molecularweight=3\times 12+6\times 1$
$\Rightarrow molecularweight=42$u
$N{H}_3$
The atomic weight of nitrogen is 14.
The atomic weight of hydrogen is 1
The number of nitrogen atoms is 1.
The number of hydrogen atoms is 3.
The molecular weight of $N{H}_3$is calculated as shown below.
$\Rightarrow molecularweight=14+3\times 1$
$\Rightarrow molecularweight=17$u
$C{H}_{3}OH$
The atomic weight of carbon is 12.
The atomic weight of hydrogen is 4.
The atomic weight of oxygen is 16.
The number of carbon atoms is 1.
The number of hydrogen atoms is 4.
The number of oxygen atoms is 1.
The molecular weight of $C{H}_{3}OH$is calculated as shown below.
$\Rightarrow molecularweight=12+4\times 1+16$
$\Rightarrow molecularweight=32$u

Note:
Make sure that if one atom is present more than one in number than the number of atoms is multiplied with the atomic weight during the calculation of molecular mass.