Question

1. how many moles of lead (ii) iodide, pbi2, are there in a 25.0 gram sample? how many atoms of lead, pb, are in the sample?

Explanation:

Step1: Find molar mass of PbI₂

Molar mass of PbI₂ = 207.2+(2×126.9)= 461 g/mol

Step2: Calculate moles of PbI₂

Moles of PbI₂ = $\frac{25.0\ g}{461\ g/mol}$≈0.0542 mol

Step3: Determine moles of Pb

In PbI₂, 1 mole has 1 mole of Pb, so moles of Pb = 0.0542 mol

Step4: Calculate atoms of Pb

Atoms of Pb = 0.0542 mol×6.022×10²³ atoms/mol = 3.26×10²² atoms

Answer:

3.26×10²² atoms