Question

73. Which of the following ion convert orange solution of K2Cr2O7 into green solution ? (1) Na2SO3 (2) Na2S (3) NaI (4) All of these

Answer 1

Explanation:

Sulfur dioxide gas turns acidified potassium dichromate (VI) solution from orange to green.

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Answer 2

The ion that converts the orange solution of K2Cr2O7 into green solution is:

(4) All of these

- The acidified solution of orange coloured K2Cr2O7 is turned into green coloured solution due to the formation of Cr2(SO4)3.

- The acidified solution of orange coloured K2Cr2O7 reacts with Na2SO3 as follows:

K2Cr2O7 + 3 Na2SO3 + 4 H2SO4 → Cr2(SO4)3 + K2SO4 + 3 Na2SO4 + 4 H2O

- The acidified solution of orange coloured K2Cr2O7 reacts with Na2S as follows:

4 K2Cr2O7 + 3 Na2SO3 + 16 H2SO4 → 4 Cr2(SO4)3 + 4 K2SO4 + 3Na2SO4 + 16 H2O

- The acidified solution of orange coloured K2Cr2O7 reacts with NaI as follows:

K2Cr2O7 + 6 NaI + 7 H2SO4 → Cr2(SO4)3 + 3 I2 + K2SO4 + 3 Na2SO4 + 7 H2O

- So, all the given compounds turn it green.