Question

How many atoms of lead are there in 10.0 g of lead?

Answer 1

The number of atoms in 10 g of Pb is 2.9064 × 10²² atoms

Step-by-step explanation:

According to Avogadro's constant, one mole of a substance contains exactly 6.02214076 × 10²³ particles such as molecules, atoms or ions.

Here we have lead, Pb, which is an uncombined element, therefore, the number of moles present in 10 g of lead can be found as follows;

Molar mass of lead = 207.2 g/mol

Mass of lead sample = 10 g

`Number \, of \, moles, \, n, \, of \, lead \, present = (Mass \, of \, lead)/(Molar \, mass \, of \, lead) = (10 \, g)/(207.2 \, g/mol) = 0.04826 \ moles`

Therefore, number of atoms in 10 g of lead is found by multiplying the number of moles by the Avogadro's number as follows;

Number of atoms = Number of moles × Avogadro's number

∴ Number of atoms in 10 g of Pb = 0.04826 × 6.02214076 × 10²³ = 2.9064 × 10²² atoms.

The number of atoms in 10 g of Pb = 2.9064 × 10²² atoms.

Answer 2

2.9 ×10^22 atoms of lead.

Step-by-step explanation:

Now, we have to make use of the Avogadro's number. Remember that according to professor Avogadro, the mole refers to the amount of substance that contains the same number of elementary entities as 12 grams of carbon-12.

The number of elementary particles (atoms, ions, molecules etc) present is one mole of a substance is equal to the Avogadro's number. Hence one mole of a substance contains Avogadro's number of elementary entities.

Now one mole of lead has a mass of 207.2 gmol-1. One mole of lead contains 6.02×10^23 atoms (Avogadro's number) of atoms.

Hence if 207.2 g of lead contains 6.02×10^23 atoms of lead

10.0 g of lead will contain 10.0 × 6.02×10^23 / 207.2 = 2.9 ×10^22 atoms of lead.

Hence 10.0g of lead contains 2.9 ×10^22 atoms of lead.