Question

The density of mercury is 13.69 g/mL. If a thermometer contains 155 micro liters of mercury, how many atoms of mercury are in the thermometer?

Answer 1

1 microliter = 1000 mL

The density of mercury $ρ = 13.69\times10^{-3}\; g/μL$

$m = V\timesρ$

$m = 155\; μL\times13.69\times10^{-3}\; g/μL = 2.12 \;g$

M(Hg) = 200.6 g/mol

$n(Hg) = \frac{m}{M} = \frac{2.12}{200.6} = 0.01 \;mol$

A mole of mercury atoms (with the formula Hg) contains 6.02×10²³ Hg atoms.

Proportion:

1 mol – 6.02×10²³ Hg atoms

0.01 mol – x

x = 6.02×10²¹ Hg atoms

Answer: 6.02×10²¹ Hg atoms