An organic compound 'A' on heating with concentrated `H_2 SO_4` forms a compound 'B' which on addition of one mole of hydrogen in presence of Ni forms a compound 'C'. One mole of compound 'C' on combustion forms two moles of `CO_2` and three moles of `H_2 O`
When 'B' and 'C' are added separately to the test tubes containing orange-brown liquid X', the colour disappears in case of 'B' but remains same in case of 'C'. The name of the liquid X and the substance responsible for colour change are respectively

Options

A. Alkaline `KMnO_4` solution and ethanoic acid
B. Alkaline `KMnO_4` and ethanol
C. Bromine water and 1, 2-dibromoethane
D. Bromine water and 1, 1, 2, 2-tetrabromoethane.

Answer

To solve the problem step by step, let's break down the information given and analyze it systematically.

### Step 1: Identify Compound A
The problem states that an organic compound 'A' is heated with concentrated sulfuric acid (H₂SO₄) to form compound 'B'. This suggests that compound 'A' is likely an alcohol, as sulfuric acid is commonly used to dehydrate alcohols to form alkenes.

**Hint:** Think about common alcohols that can undergo dehydration.

### Step 2: Formation of Compound B
When an alcohol undergoes dehydration with concentrated H₂SO₄, it typically forms an alkene. Given that compound 'B' is formed from compound 'A', we can assume that compound 'B' is likely an alkene.

For example, if we take ethanol (C₂H₅OH) as compound 'A', upon dehydration, it would form ethene (C₂H₄) as compound 'B'.

**Hint:** Consider the structure of simple alcohols and their dehydration products.

### Step 3: Hydrogenation of Compound B
Next, compound 'B' (the alkene) is treated with hydrogen in the presence of a nickel catalyst, which suggests hydrogenation. This process will convert the alkene into an alkane.

Continuing with our example, if compound 'B' is ethene (C₂H₄), adding hydrogen would yield ethane (C₂H₆) as compound 'C'.

**Hint:** Remember that hydrogenation adds hydrogen across the double bond of alkenes.

### Step 4: Combustion of Compound C
The problem states that one mole of compound 'C' on combustion produces two moles of CO₂ and three moles of H₂O. The combustion reaction can be represented as:
\[ C_xH_y + O_2 \rightarrow CO_2 + H_2O \]

For ethane (C₂H₆), the combustion reaction is:
\[ C_2H_6 + 7/2 O_2 \rightarrow 2 CO_2 + 3 H_2O \]

This matches the information given in the problem, confirming that compound 'C' is indeed ethane.

**Hint:** Use the general combustion equation to verify the products.

### Step 5: Reaction with Liquid X
The problem mentions an orange-brown liquid 'X' that reacts with compound 'B' but not with compound 'C'. The orange-brown color suggests that liquid 'X' is likely bromine water (Br₂ in water), which is known for its distinctive color.

When bromine water is added to compound 'B' (the alkene), the color disappears due to the addition reaction forming a dibrominated compound. However, since compound 'C' (the alkane) does not have a double bond, it does not react with bromine water, and the color remains unchanged.

**Hint:** Recall that alkenes react with bromine water, while alkanes do not.

### Conclusion
From the above analysis, we can conclude:
- Liquid 'X' is bromine water.
- The substance responsible for the color change is the alkene (compound 'B').

### Final Answer
The name of the liquid X is **bromine water** and the substance responsible for the color change is **compound B (the alkene)**.