Question

calculate the number of atoms in 25.0 grams of bromine, br. the mass of one mole of bromine is 79.90 g.

Explanation:

Step1: Calculate moles of Br

Moles = $\frac{\text{mass}}{\text{molar mass}}$ = $\frac{25.0\ \text{g}}{79.90\ \text{g/mol}}$

Step2: Calculate atoms using Avogadro's number

Atoms = moles × $6.022\times10^{23}\ \text{atoms/mol}$ = $\frac{25.0}{79.90}$ × $6.022\times10^{23}$

Answer:

$\approx 1.88\times10^{23}$ atoms