When `SO_2` gas is passed through acidified `K_2Cr_2O_7` solution, the colour of the solution changes to

Options

A. Red
B. Black
C. Orange
D. Green

Explanation

To solve the question about the color change of an acidified K2Cr2O7 solution when SO2 gas is passed through it, we can follow these steps:

### Step 1: Identify the reactants
The reactants in this reaction are:
- Acidified K2Cr2O7 (potassium dichromate) solution
- SO2 (sulfur dioxide) gas

### Step 2: Understand the initial color of the solution
Potassium dichromate (K2Cr2O7) in an acidified solution typically has an orange color due to the presence of Cr2O7^2- ions.

### Step 3: Reaction of SO2 with K2Cr2O7
When SO2 is passed through the acidified potassium dichromate solution, it acts as a reducing agent. The SO2 reduces the Cr2O7^2- ions to Cr^3+ ions.

### Step 4: Identify the product and its color
The reduction of Cr2O7^2- ions to Cr^3+ ions results in the formation of chromic sulfate (Cr2(SO4)3). The solution containing Cr^3+ ions typically appears green.

### Step 5: Conclusion
Thus, when SO2 gas is passed through the acidified K2Cr2O7 solution, the color of the solution changes from orange to green.

### Final Answer
The color of the solution changes to green.

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