In which case of mixing of a strong acid and a base each of `1N` concentration, temperature increase is highest ?

Options

A. 20 mL acid - 30 mL alkali
B. 10 mL acid - 40 mL alkali
C. 25 mL acid - 25 mL alkali
D. 35 mL acid - 15 mL alkali

Explanation

To determine in which case of mixing a strong acid and a base (both at 1N concentration) the temperature increase is highest, we need to analyze the heat of neutralization for each scenario. The heat of neutralization is defined as the change in enthalpy that occurs when one equivalent of an acid reacts with one equivalent of a base to form a salt and water. The more equivalents that react, the more heat is released, leading to a higher temperature increase.

Let's analyze the given options step by step:

### Step 1: Understand the given options
We have four cases of mixing a strong acid and a strong base, each with a concentration of 1N. The options are:
1. 20 ml of acid and 30 ml of base
2. 10 ml of acid and 40 ml of base
3. 25 ml of acid and 25 ml of base
4. 35 ml of acid and 15 ml of base

### Step 2: Calculate the number of milliequivalents for each case
- **Case 1**: 20 ml of acid + 30 ml of base
- Milliequivalents of acid = 20 mEq
- Milliequivalents of base = 30 mEq
- Total milliequivalents = 20 mEq (acid) + 20 mEq (base) = 20 mEq (10 mEq of base left unreacted)

- **Case 2**: 10 ml of acid + 40 ml of base
- Milliequivalents of acid = 10 mEq
- Milliequivalents of base = 40 mEq
- Total milliequivalents = 10 mEq (acid) + 10 mEq (base) = 10 mEq (30 mEq of base left unreacted)

- **Case 3**: 25 ml of acid + 25 ml of base
- Milliequivalents of acid = 25 mEq
- Milliequivalents of base = 25 mEq
- Total milliequivalents = 25 mEq (acid) + 25 mEq (base) = 25 mEq (0 mEq left unreacted)

- **Case 4**: 35 ml of acid + 15 ml of base
- Milliequivalents of acid = 35 mEq
- Milliequivalents of base = 15 mEq
- Total milliequivalents = 15 mEq (acid) + 15 mEq (base) = 15 mEq (20 mEq of acid left unreacted)

### Step 3: Compare the total milliequivalents for each case
- Case 1: 20 mEq
- Case 2: 10 mEq
- Case 3: 25 mEq
- Case 4: 15 mEq

### Step 4: Identify the case with the highest temperature increase
The highest temperature increase will occur in the case where the total number of milliequivalents of acid and base that react is the greatest. From our calculations, Case 3 has the highest total of 25 mEq.

### Conclusion
Thus, the case in which the temperature increase is highest is when **25 ml of acid is mixed with 25 ml of base**.

### Final Answer
**The correct option is: 25 ml acid and 25 ml alkali.**