Question

How do I calculate the mass of zinc and iodine that are consumed to produce zinc iodide?

Answer 1

Formation of Zinc iodide:

• The balanced chemical equation for the formation of zinc iodide is given below.

$\underset{\mathrm{Zinc}}{\mathrm{Zn}\left(\mathrm{aq}\right)}+\underset{\mathrm{Iodide}}{{\mathrm{I}}_2\left(\mathrm{aq}\right)}\to \underset{\mathrm{Zinc}\mathrm{iodide}}{{\mathrm{ZnI}}_2\left(\mathrm{aq}\right)}$

• One mole of zinc $\left(\mathrm{Zn}\right)$ reacts with one mole of iodine $\left({\mathrm{I}}_2\right)$ to form zinc iodide $\left({\mathrm{ZnI}}_2\right)$

Calculation of Masses of Zinc and Iodine:

• To calculate the mass of zinc, either mass of iodine or zinc iodide should be known.
• The mass of iodine is determined by the mass of the zinc or mass of zinc iodide.

Example:

• If the mass of Iodine is given by $12.52\mathrm{g}$.
• We know the molar mass of Iodine is $253.808\mathrm{g}.{\mathrm{mol}}^{-1}$ and that of Zinc is $65.38\mathrm{g}.{\mathrm{mol}}^{-1}$
• Here in the formation of zinc iodide, only one mole of both zinc and iodine is consumed.
• To calculate the mass of zinc consumed, we should know the steps:
• The moles of Iodine are determined by dividing its given mass by molar and it is reversed here.
• Moles of zinc can be determined by multiplying moles of iodine by the mole ratio of zinc and Iodine from the equation where zinc is in the numerator.
• Finally, the mass of zinc is determined by multiplying moles of zinc with its molar mass.

$\mathrm{Weight}\mathrm{of}\mathrm{Zinc}\left(\mathrm{Zn}\right)=12.52\mathrm{g}{\mathrm{I}}_2\times \frac{1\mathrm{mole}{\mathrm{I}}_2}{253.808{\mathrm{gmol}}^{-1}{\mathrm{I}}_2}\times \frac{1\mathrm{mole}\mathrm{Zn}}{1\mathrm{mole}{\mathrm{I}}_2}\times \frac{65.38\mathrm{g}.{\mathrm{mol}}^{-1}\mathrm{Zn}}{1\mathrm{mole}Z\mathrm{n}}$

$\mathrm{Weight}\mathrm{of}\mathrm{Zinc}\left(\mathrm{Zn}\right)=12.52\mathrm{g}{\mathrm{I}}_2\times \frac{65.38\mathrm{g}.{\mathrm{mol}}^{-1}\mathrm{Zn}}{253.808{\mathrm{gmol}}^{-1}{\mathrm{I}}_2}$

$\mathrm{Weight}\mathrm{of}\mathrm{Zinc}\left(\mathrm{Zn}\right)=12.52\mathrm{g}\times 0.258\mathrm{Zn}$

$\mathrm{Weight}\mathrm{of}\mathrm{Zinc}\left(\mathrm{Zn}\right)=3.23\mathrm{gms}$

• In the same manner, when the weight of zinc is given, we can find the weight of Iodine.

Therefore, to know the mass of zinc and iodine to be consumed, any one of their masses or mass of zinc iodide should be given.