Question

Calculate the following:
Number of bromide ions in 0.2 moles of ${\mathrm{MgBr}}_2$.

Answer 1

From the given,

The number of moles of ${\mathrm{MgBr}}_2$ is 0.2.

Step-1

$$\begin{gathered} \mathrm{Molar}\mathrm{mass}\mathrm{of}{\mathrm{MgBr}}_2=24+2\left(80\right) \\ =24+160 \\ =184\mathrm{g}/\mathrm{mol} \end{gathered}$$

Step-2

1 molecule of ${\mathrm{MgBr}}_2$ contains 2 Bromide ions.

$$\begin{gathered} \mathrm{No}.\mathrm{of}\mathrm{Bromide}\mathrm{ions}\mathrm{in}1\mathrm{mole}\mathrm{of}{\mathrm{MgBr}}_2=2\times 6.022\times {10}^{23} \\ =12.022\times {10}^{23}\mathrm{ions} \\ \mathrm{No}.\mathrm{of}\mathrm{Bromide}\mathrm{ions}0.2\mathrm{moles}\mathrm{of}{\mathrm{MgBr}}_2=0.2\times 12.022\times {10}^{23} \\ =2.4\times {10}^{23}\mathrm{ions} \end{gathered}$$

Hence, the number of bromide ions in 0.2 moles of ${\mathrm{MgBr}}_2$ is $2.4\times {10}^{23}\mathrm{ions}$.