Question

Working in the fume-hood, support a 150 mL clean and dry beaker with a wire gauze on a ring stand. Place 0.5 g of iodine in the beaker. Place an evaporating dish on top of the beaker. Place a small amount of ice in the evaporating dish. Heat the iodine in the 150 mL beaker very gently with low Bunsen burner flame.

Question: Based on the following procedues above, what is the balanced equation of the reaction involving iodine? Equation must include the state of of each participant in the reaction.

Answer 1

The given experiment if complete is the purification of iodine by sublimation. Here there occurs no chemical change but only physical change. Therefore any reactions used to represent the changes only involve a change in state of the materials.

Iodine on heating sublimes owing to its high vapor pressure and crystallizes on the cooler zone - the evaporating dish with ice. This can be represented as I_{2 (s)} -- heat --> I_{2 (g)} -- cool --> I_{2 (s)}

The next change is the melting of the ice on the evaporating dish due to heat transfer from the iodine vapors as the latter crystallizes on the underside of the dish. This is given as H₂O _(s) -- heat --> H₂O _(l)