A block of lead weighs 11.3 grams. How many atoms of lead are in this sample? • Use 6.022 x 1023 mol
for Avogadro's number.

11.3 g block of lead contains 3.29×10²² atoms

From Avogadro's hypothesis, we understood that 1 mole of any substance contains 6.022×10²³ atoms. Thus,

1 mole of lead = 6.022×10²³ atoms

Recall:

1 mole of lead = 207 g

Thus,

With the above information in mind, we can obtain the number of atoms in 11.3 g block of lead as illustrated below:

207 g of lead = 6.022×10²³ atoms

Therefore,

11.3 g of lead = (11.3 × 6.022×10²³) / 207

Thus, 11.3 g block of lead contains 3.29×10²² atoms

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To get the number of atoms in this sample, we first need the number of moles of lead in 11.3 grams

Number of moles of Lead:

Molar mass of lead = 207 grams / mol

Number of moles  = given mass / molar mass

Number of moles = 11.3 / 207

Number of moles = 0.05 moles

Number of atoms of lead in 11.3 gram sample:

Number of atoms = Number of moles * avogadro's number

Number of atoms = 0.05 * 6.022 * 10²³

Number of atoms = 5 * 10⁻² * 10²³ * 6.022

Number of atoms = 30.11 * 10²¹