Question

What is the mass, in grams, of a sample of 1.72 × 1023 atoms of potassium (K)? Show your work or explain the steps that you used to determine your answer.

Answer 1

According to the Avogadro's Constant, 1 mole of substance has 6.02214086 × 10²³ (Unit is mol⁻¹) particles.

This means, 1 mole = 6.02214086 × 10²³ molecules / atoms

Given K atoms = 1.72 x 10²³

Moles of K = 1.72 x 10²³ / 6.02214086 × 10²³ mol⁻¹

= 0.286 mol

Moles (mol) = mass (g) / molar mass (g/mol)

Molar mass of K = 39.1 g/mol
Mass of K = 0.286 mol x 39.1 g/mol
= 11.18 g

Hence, 1.72 x 10²³ of K atoms have 11.18 g of mass.