Question

Calcium carbonate has the chemical formula CaCO3. A certain quantity of calcium carbonate has 8.35x1025 atoms. How many moles of calcium carbonate is the sample?

Answer 1

Answer

27.7 moles

Explanation:

Data Given:

Chemical formula of Calcium carbonate = CaCO₃

no. of atoms of CaCO₃ = 8.35 x 10²⁵ atoms

moles of CaCO₃= ?

Solution

First convert number of atoms to number of molecules

As

we have 5 atoms per molecule then how many molecules will be for 8.35 x 10²⁵ atoms

So, apply unity formula

               5 atoms  ≅ 1 molecule of CaCO₃

               8.35 x 10²⁵ atoms  ≅ X molecule of CaCO₃

by doing cross multiplication

      X molecule of CaCO₃ = 8.35 x 10²⁵ atoms x 1 molecule / 5 atoms

      X molecule of CaCO₃ = 1.67 x 10²⁵  molecule

Formula will be used

           no. of moles = no. of molecules / Avogadro's number . . . . (1)

Where

Avogadro's number = 6.022 x 10²³ molecules/mol

So,

Put values in equation 1

          no. of mole = 1.67 x 10²⁵/ 6.022 x 10²³ (molecules/mol)

          no. of mole = 27.7 moles

So,

moles of CaCO₃ = 27.7 moles