Question

Calculate the number of oxygen atoms in the following compound:
a. 20g of CaCO3
b. 10 moles of CaCO3​

Answer 1

Answer:

a) 3.6132*10²³ b) 1.8066*10²5

Explanation:

a) no. of O atoms

=no.of molecules*total no. of oxygen atoms

=moles*NA*total no. of oxygen atoms

=20/100*6.022*10²³*3

=1/5*6.022*10²³*3

=6.022*10²³*3/5

=18.066*10²³/5

=3.6132*10²³

b) no. of O atoms

=no.of molecules*total no. of O atoms

=moles*NA*total no. of molecules

=10*6.022*10²³*3

=6.022*3*10²³*10

=18.066*10²⁴

=1.8066*10²5

Answer 2

We have to calculate the number of oxygen atoms in the following compound

(a) 20g of CaCO3

(b) 10 moles of CaCO3

Solution : we see in one molecule of CaCO3 compound, three atoms of oxygen is present.

(a) 20g of CaCO3

Given weight of CaCO3 = 20g

Molecular weight of CaCO3 = 100g/mol

so, no of moles of CaCO3 = 20/100 = 0.2

so no of moles of Oxygen atom in CaCO3 = 3 × 0.2 = 0.6

no of oxygen atoms in CaCO3 = no of moles × Avogadro's number

= 0.6 × 6.022 × 10²³

= 3.6132 × 10²³

(b) 10 moles of CaCO3

so, no of moles of oxygen atoms in CaCO3 = 3 × 10 = 30 moles

no of oxygen atoms in CaCO3 = no of moles of oxygen atoms × Avogadro's number

= 30 × 6.022 × 10²³

= 180.66 × 10²³

= 1.8066 × 10²⁵