Question

What is the mass of 3 molecules of CCl4

Answer 1

For this I think it makes sense to express the mass in atomic mass units (AMU). Protons and neutrons each have a mass of 1 AMU, but rather than just adding protons and neutrons for each atom, we can just use their atomic masses directly.

C = ~12 AMU
Cl = ~35 AMU

CCl4 = (1 x 12) + (4 x 35) = 152 AMU

3 x CCl4 = 3 x 152 = 456 AMU