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

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

here we have to get the change of moles on decrease the volume of the reaction in gas phase.

the   per the given options it will decrease by (d) 11-50%

we know, on decreasing the volume of the gas phase reaction the reaction moves to the product side.

the reaction:                     so₂cl₂ (g) = so₂ (g) + cl₂ (g)         total

the moles at equilibrium:   1 - α                 α               α           = 1+α

concentrations:                   1 - α               α               α           = 1 + α

(concentration = moles/volume, as volume is 1 l)

(where α is the degree of dissociation)

now the dissociation constant in terms of concentration is :

=  

or,

or,   = (at v = 1l)

the reaction:                     so₂cl₂ (g) = so₂ (g) + cl₂ (g)         total

the moles at equilibrium:   1 - α                 α               α           = 1+α

concentrations:               (1 - α)/0.5           α/0.5         α/0.5       = (1 + α)/0.5

thus, the dissociation constant in terms of concentration is :

or,  

=  

so, the change of 1 : 1/0.5

or, 1: 2

thus it will decrease by 50%.

or, as per the given options it will decrease by 11-50%

- lead + phosphoric acid = hydrogen + lead(ii) phosphate