Question

how many molecules are in 2.1 moles of hbr? lets complete the conversion factor first. $\frac{?\text{ molecules of hbr}}{1\text{ mol hbr}}$ 6.23×10²⁰ 6.02×10²³ 6.12×10²⁴

Explanation:

Step1: Recall Avogadro's number

1 mole of any substance contains $6.02\times 10^{23}$ molecules. So the conversion factor is $\frac{6.02\times 10^{23}\text{ molecules of HBr}}{1\text{ mol HBr}}$.

Step2: Calculate number of molecules in 2.1 moles

Multiply the number of moles by the conversion factor. Number of molecules $=2.1\text{ mol}\times\frac{6.02\times 10^{23}\text{ molecules}}{\text{mol}} = 1.2642\times 10^{24}$ molecules. But the key here is identifying the conversion - factor value which is $6.02\times 10^{23}$ molecules per mole.

Answer:

$6.02\times 10^{23}$