Question

Calculate the number of O2 oxygen atoms in 20g of CaCO3

Answer 1

The number of O2 oxygen atoms in 20g of CaCO3 would be 1.8069*10 ²³  atoms

Explanation:

molecular weight of CaCO3 =    Molecular weight of Ca +  Molecular weight of C + 3* Molecular weight of O

= 40 + 12 + 3*16

= 100 g/mol

now 20 g of CaCO3 has 20 / 100 moles of CaCO3  

 // (as moles = mass/molecular mas  )

or ;

0.2 moles of CaCO3

now 1 mole of CaCO3  has 3 *16 = 48 g of O // as CaCO3 has 3 O

0.2 mole of CaCO3  will have  *0.2* 48 g = 9.6 g of Oxygen  

1 oxygen molecule O2 has molecular weight of 32 g/mol

9.6 g of oxygen will have = 9.6/32 molecules of oxygen

                                        = 0.3 molecules of oxygen

till now we calculated that

20 gram of CaCO3 will have 0.3 molecules of oxygen

1 molecule  has 6.023 * 10 ²³ atoms

0.3 molecule will have = 0.3*  6.023 * 10 ²³ atoms

                                        = 1.8069*10 ²³  atoms