Question

An atom of neon has a mass of $3.35\times {10}^{-23}g$. How many atoms of neon are there in 20 g of the gas?

Answer 1

Apply unitary method

$3.35\times {10}^{-23}g$ contains $1$ atom of neon

$\therefore$ $1g$ contain $\frac{1}{3.35\times {10}^{-23}}$ atoms of neon

$\therefore$ $20g$ contains $20\times \frac{1}{3.35\times {10}^{-23}}$ atoms of neon

$=5.97\times {10}^{23}$ atoms of neon