A student adds dilute sulphuric add to lime water. Will the reaction mixture become hot or cold ? Why ?

Answer

To determine whether the reaction mixture becomes hot or cold when dilute sulfuric acid is added to lime water, we can follow these steps:

### Step 1: Identify the Reactants
The reactants in this scenario are:
- Dilute sulfuric acid (H₂SO₄)
- Lime water, which is a solution of calcium hydroxide (Ca(OH)₂)

### Step 2: Write the Chemical Reaction
When dilute sulfuric acid is added to lime water, a chemical reaction occurs. The balanced chemical equation for this reaction is:
\[ \text{H}_2\text{SO}_4 + \text{Ca(OH)}_2 \rightarrow \text{CaSO}_4 + \text{H}_2\text{O} \]
This means that sulfuric acid reacts with calcium hydroxide to produce calcium sulfate (CaSO₄) and water (H₂O).

### Step 3: Classify the Reaction
This reaction is a type of neutralization reaction, where an acid reacts with a base to form a salt and water.

### Step 4: Determine the Nature of the Reaction
Neutralization reactions are typically exothermic, meaning they release energy in the form of heat. In this case, the reaction releases energy because:
- The hydrogen ions (H⁺) from the sulfuric acid combine with the hydroxide ions (OH⁻) from the lime water to form water (H₂O).
- The formation of water involves the creation of covalent bonds, which releases energy.

### Step 5: Conclusion
Since the reaction is exothermic, the reaction mixture will become hot. Therefore, when dilute sulfuric acid is added to lime water, the test tube will feel warm to the touch.

### Final Answer
The reaction mixture will become hot because the reaction is exothermic, releasing energy in the form of heat.

---