Question Video: Identifying the Reason for Melting Zinc Iodide before Beginning Electrolysis from a Set of Reasons | Nagwa Question Video: Identifying the Reason for Melting Zinc Iodide before Beginning Electrolysis from a Set of Reasons | Nagwa

Question Video: Identifying the Reason for Melting Zinc Iodide before Beginning Electrolysis from a Set of Reasons Chemistry • Third Year of Secondary School

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In a laboratory demonstration of the electrolysis of zinc iodide, a teacher melts the compound before turning on the electricity. What is the reason for this step in the procedure?

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Video Transcript

In a laboratory demonstration of the electrolysis of zinc iodide, a teacher melts the compound before turning on the electricity. What is the reason for this step in the procedure? (A) Melting the salt ensures a good rate of reaction. (B) This step ensures good connections between the substance and the electrodes. (C) The reaction is exothermic. (D) The zinc and iodide ions must be free to move. Or (E) this step removes water molecules adhering to the zinc iodide powder.

Electrolysis is a chemical process where electricity is passed through an electrolyte, causing it to decompose into its constituent elements. A simple electrolytic cell can be set up using two electrodes and a DC power supply which drives an electric current through the electrodes which are placed into a substance known as the electrolyte.

For the reaction to proceed long enough to produce our products, we need a continuous flow of electrons to move around the circuit. And the electrolyte is a substance, or mixture, that contains mobile ions that can undergo electrolysis by allowing a current to flow. We need the ions in the electrolyte to be able to move in order for this to happen.

In the example in the question, the substance we are examining is zinc iodide. We are not told that we are dissolving the zinc iodide in water. In fact, the teacher melts the zinc iodide, so what we have here is a molten solution. In the molten state, the ions are mobile so the current can be carried between the two electrodes. This would be impossible if the zinc iodide were in a solid state.

If we examine our answer choices, we can see that the correct answer choice is (D). The zinc and iodide ions must be free to move.

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