Question

What is the amount of ${{\text{H}}_2}{\text{S}}{{\text{O}}_4}$ (in grams) present in $0.2{\text{moles}}$ of sulfuric acid?

Answer 1

Hint: A mole is simply a unit of measurement. One mole of a molecule has $6.02 \times {10^{23}}$ atoms. This particular number is called Avogadro number. Relative atomic mass of an element in the periodic table is the mass of one mole of that atom. In the case of molecules, composition is given by its molecular formula.

Complete step by step answer:
Concentration is the amount of solute dissolved in a given amount of solution. There are different types of concentration units. Formula and molecular mass deal with individual atoms and molecules. Mole is the unit that relates the number of particles and mass.
It is given that the number of moles of ${{\text{H}}_2}{\text{S}}{{\text{O}}_4}$, ${\text{n}} = 0.2{\text{mol}}$
${{\text{H}}_2}{\text{S}}{{\text{O}}_4}$ contains two hydrogen, one sulfur and four oxygen atoms. Thus molar mass of ${{\text{H}}_2}{\text{S}}{{\text{O}}_4}$ is equal to the sum of atomic masses of these three atoms.
Atomic mass of hydrogen, ${{\text{m}}_{\text{H}}} = 1{\text{u}}$
Atomic mass of sulfur, ${{\text{m}}_{\text{S}}} = 32.065{\text{u}}$
Atomic mass of oxygen, ${{\text{m}}_{\text{O}}} = 16{\text{u}}$
From the above values, we can calculate the molar mass or molecular mass.
Molecular mass of ${{\text{H}}_2}{\text{S}}{{\text{O}}_4}$, ${{\text{M}}_{{{\text{H}}_2}{\text{S}}{{\text{O}}_4}}} = 2 \times 1{\text{u}} + 1 \times 32.065{\text{u}} + 4 \times 16{\text{u}}$
Simplifying, we get
${{\text{M}}_{{{\text{H}}_2}{\text{S}}{{\text{O}}_4}}} = 2 + 32.065 + 64 = 98.065{\text{gmo}}{{\text{l}}^{ - 1}}$
Number of moles, ${\text{n}}$ can be calculated by dividing mass, ${\text{w}}$ by molar mass, ${\text{M}}$.
i.e. ${\text{n}} = \dfrac{{\text{w}}}{{\text{M}}}$
Substituting the values of ${\text{n}}$ and ${\text{M}}$, we get
$0.2{\text{mol}} = \dfrac{{\text{w}}}{{98.065{\text{gmo}}{{\text{l}}^{ - 1}}}}$
Thus the amount of sulfuric acid in grams, ${\text{w}} = 0.2{\text{mol}} \times 98.065{\text{gmo}}{{\text{l}}^{ - 1}} = 19.613{\text{g}}$.
Hence the amount of ${{\text{H}}_2}{\text{S}}{{\text{O}}_4}$ in grams present in $0.2{\text{moles}}$ of sulfuric acid is $19.613{\text{g}}$.

Additional information:
Molar mass is the collective name for atomic mass and molecular mass. We use moles to calculate the number of particles, molecules, concentrations, etc. It represents a very large quantity of items.

Note:
Moles relate the mass of a single atom in ${\text{amu}}$ to the mass in grams. Moles to atoms or molecules conversions can be done by multiplying with Avogadro number. Atoms or molecules to moles conversions can be done by dividing by Avogadro number. Moles to grams conversion is moles times molar mass.