Question

How many atoms of carbon present in 3.9g of benzene​

Answer 1

no. of carbon atoms = 1.806 × 10²³

Step-by-step explanation:

The question asks us to find the number of atoms in 3.9 g of benzene.

To do this we must know that the chemical formula of benzene is C₆H₆.

Therefore, the molecular mass of benzene is:

R.M.M = (12 × 6) + (1 × 6)

= 72 + 6

= 78

Now that we know the molecular mass of benzene, we have to find the number of moles of benzene in 3.9 g of benzene:

no. of moles =
`\mathrm{(mass)/(R.M.M)}`

=
`(3.9)/(78)`

= 0.05 mol

From the number of moles, we can find the number of molecules of benzene using the formula:

`\boxed{\mathrm{no. \ of \ molecules = no. \ of \ moles * Avogadro's \ number}}`

where Avogadro's number = 6.02 × 10²³

Therefore,

no. of molecules of benzene = 0.05 × 6.02 × 10²³

= 3.01 × 10²²

Since each molecule of benzene contains 6 atoms of carbon, we have to multiply the number of benzene molecules by 6:
no. of carbon atoms = 3.01 × 10²² × 6

= 1.806 × 10²³

Therefore, there are 1.806 × 10²³ atoms of carbon in 3.9 g of benzene.