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* 10^(23)`

Number of moles of tungsten =
`(number of atoms)/(Avogadro number)`

number of moles =
`(2.1* 10^(24)atoms)/(6.022* 10^(23) atoms/mol)`

=
`0.3487* 10 mole\simeq 3.49 mole`

Therefore, 1 mole of tungsten consist of
`6.022* 10^(23)` atoms

So,
`3.49 mole` of tungsten consist of
`2.1* 10^(24)` atoms.

Number of moles is also equal to
`(mass in g)/(molar mass)`

`3.49 mole =(mass in g)/(183.84 g/mol)`

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

=
`641.6016 g` or
`6.4* 10^(2) g`

Thus, mass in g of
`2.1* 10^(24)atoms` =
`6.4* 10^(2) g`.