Assertion: If `H_(2)` and `Cl` enclosed separately in the same vessel exert pressure of `100` and `200 mm` respectively, their mixture in the same vessel at the same temperature will exert a pressure of `300 mm`
Reason: Dalton's law of partial pressures states that total pressure is the sum of partial pressures.

Options

A. if both assertion and reason are true and reason is thr correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reson are false.

Explanation

To solve the question, we will analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that if hydrogen (H₂) and chlorine (Cl₂) are enclosed separately in the same vessel and exert pressures of 100 mm and 200 mm respectively, their mixture in the same vessel at the same temperature will exert a pressure of 300 mm.

### Step 2: Apply Dalton's Law of Partial Pressures
Dalton's Law of Partial Pressures states that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas.

### Step 3: Calculate the Total Pressure
According to Dalton's Law:
- Pressure exerted by H₂ (P₁) = 100 mm
- Pressure exerted by Cl₂ (P₂) = 200 mm

Total Pressure (P_total) = P₁ + P₂
P_total = 100 mm + 200 mm = 300 mm

### Step 4: Conclusion
Since the total pressure exerted by the mixture of hydrogen and chlorine is indeed 300 mm, the assertion is correct.

### Step 5: Analyze the Reason
The reason provided states that Dalton's law of partial pressures states that the total pressure is the sum of partial pressures. This is true and supports the assertion.

### Final Answer
Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct conclusion is that both statements are true.