Question

Calculate the mass (in g) of 2.1×1024 atoms of w. Calculate the mass (in ) of atoms of . 1.5 ×102g 3.9×102g 2.4 ×102g 6.4 ×102g 3.2 ×102g

Answer 1

$W$ is the symbol of tungsten.

Molar mass of $W$  = $183.84 g/mol$

Now, number of atoms are converted to number of moles by Avogadro number i.e. $6.022\times 10^{23}$

Number of moles of tungsten  =$\frac{number of atoms}{Avogadro number}$

number of moles  = $\frac{2.1\times 10^{24}atoms}{6.022\times 10^{23} atoms/mol}$

= $0.3487\times 10 mole\simeq 3.49 mole$

Therefore,  1 mole of tungsten consist of  $6.022\times 10^{23}$ atoms

So,  $3.49 mole$ of tungsten consist of $2.1\times 10^{24}$ atoms.

Number of moles is also equal to $\frac{mass in g}{molar mass}$

$3.49 mole =\frac{mass in g}{183.84 g/mol}$

$mass in g =\frac{3.49 mole\times 183.84 g/mol}$

= $641.6016 g$ or $6.4\times 10^{2} g$

Thus, mass in g of $2.1\times 10^{24}atoms$ = $6.4\times 10^{2} g$.