Question

KI or Nal

1- Can you easily determine the identities of the products formed on the electrodes based on the first part of this experiment (without starch)? Explain.

2. A. In the second part, why does the starch added to the solution change color?

B. How does the starch help in identifying the product of the oxidation reaction and the chemical species being oxidized?

3. Write the equation for the redox reaction taking place at the anode.

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4. Write the equation for the redox reaction taking place at the cathode.

Answer 1

1) No, we cannot easliy determine the products without the addition of starch

2) A) The addition of starch helps because since KI acts as a indicator for starch, which will change the color of the solution to blue which will detect the presence of KI or potassium iodide in the soluution

B) Because of blue color imparted which is of I2 gas, we can distinguis the reaction happening at the cathode and anode

3) Reaction at anode

2I- ------> I2(g) + 2e-

The negatively charged iodine ions will be conveted into I2 gas

4) Reaction at cathode

I2 (g) + I- -----> I3-