Calculate the number of atoms in : (i) 0.02 moles of carbon (ii) 30 grams of carbon (iii) 6 moles of aluminium ions


#1

(i) We know that,
1 mole of atoms contain = 6.022 x 10^23 atoms.
Therefore,
1 mole of carbon atoms
= 6.022 x 10^23 carbon atoms.

and, 0.02 moles of carbon
= 6.022 x 10^23 x 0.02 atoms.
= 1.2 x 10^22 atoms.

(ii) We know that, gram atomic mass = 1 mole
Therefore,
12 grams of carbon = 1 mole
and, 1 gram of carbon = 1/12 mole
So, 30 grams of carbon = 1/12 x30 = 2.5 moles

Now, 1 mole of atoms contain 6.022 x 10^23 atoms
Therefore,
1 mole of carbon atoms
= 6.022 xio23 carbon atoms,

and 2.5 moles of carbon
= 6.022 x 10^23 x 2.5 carbon atoms.
= 1.50 x 10^24 carbon atoms.

(iii) 1 mole of Al3+ ions contain = 6.022 x 10^23 atoms
Therefore,
6 moles of Al3+ ions contain
= 6 x 6.022 x 10^23 atoms
= 3.61 x 10^24 atoms