Question

One mole of any substance contains $6.022\times {{10}^{23}}$ atoms/molecules. Number of molecules of ${{H}_{2}}S{{O}_{4}}$ present in 100 ml of 0.02 M ${{H}_{2}}S{{O}_{4}}$ solution is………. molecules.
A. $12.044\times {{10}^{20}}$
B. $6.022\times {{10}^{23}}$
C. $1\times {{10}^{23}}$
D. $12.044\times {{10}^{23}}$

Answer 1

First we have to calculate the number of moles of the chemical from molarity and volume by using the following formula.
Number of moles of the chemical = (molarity of the chemical) (Volume of the solution in liter)
Later by using the number of moles we can calculate the number of molecules by using the below formula.
Number of molecules of the chemical = (number of moles of the chemical) (Avogadro number)
Avogadro number = $6.022\times {{10}^{23}}$ atoms/molecules

Complete step-by-step answer: - In the question it is given to calculate the number of molecules of sulphuric acid present in 100 ml of 0.02 M solution.
- First we have to calculate the number of moles of sulphuric acid by using the below formula.
Number of moles of the chemical = (molarity of the chemical) (Volume of the solution in liter)
= (0.02) ( 0.1) = 0.002 molecules.
- Now we have to calculate the number of sulphuric acid molecules by using the below formula.
Number of molecules of the chemical = (number of moles of the chemical) (Avogadro number)
= (0.002) ($6.022\times {{10}^{23}}$) = $12.044\times {{10}^{20}}$ molecules
- Therefore the number of molecules present in 100 ml of 0.02 M sulphuric acid is $12.044\times {{10}^{20}}$ molecules.

So, the correct option is A.

Note: To know about the number of atoms in a molecule we have to use the Avogadro number at the same time we can use the Avogadro number to find the number of molecules in a known concentration of the solution.