Question

How many atoms are in 15.3 cm3 of mercury (at room temperature)?

Answer 1

1cm^3 = 1 mL

You need to convert to moles and multiply by Avogadro's number.

so convert from mL to grams by determine Mercuries density (wolfram alpha or chemspider can tell you these properties).

you will have to multiply the mL of mercury by the density of mercury to get the grams of mercury

then you have to divide the grams by the molecular mass to get the moles than multiply by avagadros number