Equal volumes of two jars contain HCl, `NH_3` gases respectively at constant temperature and pressure P. When one of the jars is inverted over another jar so that they mix up, the pressure in either of the jars is

Options

A. 1 atm
B. Equal to P
C. Becomes Zero
D. P + P = 2P

Answer

To solve the problem, let's break it down step by step:

### Step 1: Understand the Gases Involved
We have two gases: hydrochloric acid (HCl) and ammonia (NH₃). Both are in equal volumes in separate jars at constant temperature and pressure.

**Hint:** Identify the properties of the gases involved, especially their reactivity.

### Step 2: Mixing the Gases
When one jar containing NH₃ is inverted over the jar containing HCl, the two gases will mix.

**Hint:** Consider what happens when two reactive gases are combined.

### Step 3: Reaction Between HCl and NH₃
Upon mixing, HCl and NH₃ will react to form ammonium chloride (NH₄Cl), which is a solid. The reaction can be represented as:
\[ \text{NH}_3(g) + \text{HCl}(g) \rightarrow \text{NH}_4\text{Cl}(s) \]

**Hint:** Recall the products of the reaction between ammonia and hydrochloric acid.

### Step 4: Effect on Pressure
Since NH₄Cl is a solid, it will precipitate out of the gas phase. This means that the number of gas molecules decreases significantly because the gaseous reactants are converted into a solid product.

**Hint:** Think about how the change in the number of gas molecules affects the pressure in the container.

### Step 5: Conclusion on Pressure
According to the ideal gas law, if the number of gas molecules decreases, the pressure in the container will also decrease. In this case, since all the gaseous reactants have been converted into a solid, the pressure will drop to zero.

**Hint:** Consider the implications of the ideal gas law (PV=nRT) when the number of moles of gas (n) approaches zero.

### Final Answer
The pressure in either of the jars after the gases mix and react will be 0.

**Correct Option:** C) 0