Question

What will be the mass of 5 moles of $S{O_2}$ ?

Answer 1

Hint : $S{O_2}$ is a triatomic molecule. It is made up of one atom of sulphur and 2 atoms of oxygen.
To find out the molecular mass of any molecule we will have to add the atomic mass of the constituent atoms together.
1 mole of any substance will contain $6.022 \times {10^{23}}{\text{ }}$ atoms or molecules. So to find the mass of 5 moles of $S{O_2}$ , we have to find the mass of one mole first.

Complete Step By Step Answer:
To find the mass of one molecule of $S{O_2}$ we have to add the mass of one atom of sulphur and two atoms of oxygen.
This will give us the molecular weight of $S{O_2}$
Mass of $S{O_2}$ = Mass of ${\text{S }}$ + $2 \times$ Mass of ${\text{O}}$
Since mass of sulphur is 32 ${\text{ g/mol}}$ and mass of oxygen is 16 ${\text{ g/mol}}$
$\Rightarrow 32 + 2 \times 16$
$\Rightarrow 32 + 32$
$\Rightarrow 64{\text{ g/mol}}$
The mass of 1 mole of any substance is equal to that substance's molecular weight.
Thus we can say that each mole of $S{O_2}$ weighs 64 grams.
Now we have to find out the mass of 5 moles of $S{O_2}$
Since 1 mole of $S{O_2}$ weighs $64{\text{ g/mol}}$
We can say that 5 moles of $S{O_2}$ weighs
$\Rightarrow 5{\text{ moles }} \times 64{\text{ g/mol}}$
$\Rightarrow 320{\text{ grams}}$
Therefore the mass of 5 moles of $S{O_2}$ is 320 grams.

Note :
Since each mole of a substance contain $6.022 \times {10^{23}}$ atoms or molecules or ions, we can say that 1 mole of $S{O_2}$ contains $6.022 \times {10^{23}}$ molecules of sulphur dioxide.
So 5 moles of $S{O_2}$ will contain 5 times the number molecules as in 1 mole of $S{O_2}$
This means that 5 moles of $S{O_2}$ contains
$\Rightarrow 5 \times 6.022 \times {10^{23}}{\text{ S}}{{\text{O}}_2}{\text{ molecules }}$
$\Rightarrow 30.11 \times {10^{23}}{\text{ S}}{{\text{O}}_2}{\text{ molecules}}$
While dealing with problems involving moles, always make sure to apply these concepts.