Question

Calculate the no.of iron atoms in a piece of iron weighing 2.8g

Answer 1

Number of moles is given by the formula :

Number of moles = Given mass of substance / molar mass

Here given mass = 2.8 g

And molar mass = 56 g per mole

Number of moles of iron present in 2.8 g will be

Number of moles = 2.8 / 56

⇒ Number of moles = 0.05

Hence number of moles of iron present in 2.8 g is 0.05.

We know 1 mole of any substance contain 6.022 × 10²³

Therefore 1 mole of iron contain = 6.022 × 10²³ atoms

⇒ 0.05 moles of iron contain = 6.022 × 10²³ × 0.05 atoms

⇒ 0.05 moles of iron contain = 0.301 × 10²³ atoms

Therefore 2.8 g of iron contains 3.011 × 10²² atoms