The mass in grams of 2.75 x 1021atoms of Li is.

a.

0.3017 g

c.

3.017 g

b.

0.0317 g

d.

0.00317 g

The mass in grams of 2.75 x10^21 is calculated as

by use of avogadros law

1mole = 6.02 x 10 ^23 atoms

what of 2.75 x 10^23 atom

2.75 x 10^21atoms x 1mole / 6.02 x 10^23 = 4.568 x10 ^-3moles

mass is therefore = moles x molar mass of lithium (6.941)

that is (4.568 x 10^-3) x 6.941 = 0.0317 grams