Mass of 2 10^21 number of atoms of an element is 0.4g . What is the mass of 0.5 mole of the element ? [1+1]

To find the mass of 0.5 mole of the element, we follow these steps:

1. Calculate the molar mass of the element: Given:

   • Number of atoms = $2\times 10^{21}$
   • Mass of atoms = 0.4 g

   Moles of atoms = $\frac{\text{Number of atoms}}{\text{Avogadro’s number}}=\frac{2\times 10^{21}}{6.022\times 10^{23}}=3.32\times 10^{-3}$ moles.

   Molar mass ($M$) = $\frac{\text{Mass}}{\text{Moles}}=\frac{0.4\text{ g}}{3.32\times 10^{-3}\text{ moles}}=120.5\text{ g/mol}$.

2. Calculate the mass of 0.5 mole of the element: Mass = Moles × Molar mass = $0.5\text{ moles}\times 120.5\text{ g/mol}=60.25\text{ g}$.

The mass of 0.5 mole of the element is 60.25 g.