20. The mass of one mole of lead (Pb) atoms is 207.2 g. Use a proportion to calculate the n

lead atoms in a 15.00 g sample of lead.

2. Y

i n the mathematical relationship between atomic mass units (amu) and grams (g) ?

a) atoms Pb = 4.3595 E22 amu

b) g = (6.022 E23 amu) * (Mw)

Explanation:

m Pb = 207.2 g / mol Pb

sample:

∴ m = 15.00 g

a) atoms Pb = ?

1 mol ≡ 6.022 E23 amu

⇒ atoms Pb = (15.00g Pb) (mol Pb/207.2 g) (6.022 E23 amu/mol)

⇒ atoms Pb = 4.3595 E22 amu

b) relationship:

∴ 1 mol (n) ≡ 6.022 E23 amu ... (1)

∴ mass (g) ≡ (Mw) * (n)

⇒ n = g / Mw ... (2)

∴ Mw: molecular weight

(1) = (2):

⇒ g / Mw ≡ 6.022 E23 amu

⇒ g ≡ (6.022 E23 amu) * (Mw)