Question

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?​

Answer 1

The mass of 0.5 moles of the element : 60.241 g

Further explanation

Given

mass of 2 x 10²¹ number of atoms of an element is 0.4 g

Required

the mass of 0.5 mole

Solution

Find relative atomic mass of the element(Ar)

mol of 2 x 10²¹ atoms :

$\tt n=\dfrac{N}{No}=\dfrac{2.10^{21}}{6.02.10^{23}}=3.32.10^{-3}$

$\tt Ar=\dfrac{mass}{mol}=\dfrac{0.4}{3.32.10^{-3}}=120.482$

the mass of 0.5 moles :

$\tt mass=mol\times Ar\\\\mass=0.5\times 120.482=60.241~g$