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Grade 9Thermal Physics

A vessel of volume 30 l is seprated into three equal parts by stationary semipermeable thin member as shown in the fig.the left middle and right parts are filled with hydrogen =30gm mass of oxygen is 160 gm and of nitrogen is 70 . the left partition lets through only hydrogen ,while the right partition lets through hydrogen and nitrogen. what will be the presssure in each part of vessel after the equilibrium has been set in if the vessel is kept at constant temp T=300k
fig

Profile image of Jitender Pal
12 Years agoGrade 9
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ApprovedApproved Tutor Answer1 Year ago

To determine the pressure in each part of the vessel after equilibrium has been established, we need to apply the principles of gas laws and the behavior of gases in relation to their partial pressures. Given that the vessel is divided into three equal parts, each with a volume of 10 liters, we can analyze the situation step by step.

Understanding the Setup

The vessel has three compartments:

  • Left compartment: Contains only hydrogen (30 g)
  • Middle compartment: Contains oxygen (160 g)
  • Right compartment: Contains nitrogen (70 g) and hydrogen (which can diffuse from the left compartment)

Calculating Moles of Each Gas

First, we need to convert the mass of each gas into moles using the molar mass:

  • Molar mass of hydrogen (H₂) = 2 g/mol
  • Molar mass of oxygen (O₂) = 32 g/mol
  • Molar mass of nitrogen (N₂) = 28 g/mol

Now, we calculate the moles:

  • Moles of hydrogen: \( n_H = \frac{30 \text{ g}}{2 \text{ g/mol}} = 15 \text{ mol} \)
  • Moles of oxygen: \( n_O = \frac{160 \text{ g}}{32 \text{ g/mol}} = 5 \text{ mol} \)
  • Moles of nitrogen: \( n_N = \frac{70 \text{ g}}{28 \text{ g/mol}} = 2.5 \text{ mol} \)

Applying Dalton's Law of Partial Pressures

Dalton's Law states that the total pressure in a mixture of gases is equal to the sum of the partial pressures of each individual gas. The partial pressure can be calculated using the ideal gas law:

PV = nRT, where:

  • P = pressure
  • V = volume
  • n = number of moles
  • R = ideal gas constant (0.0821 L·atm/(K·mol))
  • T = temperature in Kelvin (300 K)

Calculating Pressures in Each Compartment

1. **Left Compartment (Hydrogen only)**:

Using the ideal gas law:

Pressure \( P_H = \frac{n_H \cdot R \cdot T}{V} = \frac{15 \cdot 0.0821 \cdot 300}{10} = 36.945 \text{ atm} \)

2. **Middle Compartment (Oxygen only)**:

Pressure \( P_O = \frac{n_O \cdot R \cdot T}{V} = \frac{5 \cdot 0.0821 \cdot 300}{10} = 12.315 \text{ atm} \)

3. **Right Compartment (Hydrogen and Nitrogen)**:

Initially, the right compartment has no hydrogen, but it will gain hydrogen from the left compartment. At equilibrium, the partial pressures will adjust based on the diffusion of hydrogen into this compartment. The total moles in the right compartment will be the sum of the moles of nitrogen and the moles of hydrogen that have diffused.

Let’s assume that at equilibrium, \( x \) moles of hydrogen diffuse into the right compartment:

  • Moles of hydrogen in the right compartment = \( x \)
  • Total moles in the right compartment = \( x + 2.5 \)

Using the ideal gas law for the right compartment:

Pressure \( P_R = \frac{(x + 2.5) \cdot R \cdot T}{10} \)

Equilibrium Condition

At equilibrium, the partial pressures of hydrogen in the left and right compartments will be equal. Thus:

Pressure of hydrogen in the left compartment = Pressure of hydrogen in the right compartment

36.945 atm = \( \frac{x \cdot 0.0821 \cdot 300}{10} \)

Solving for \( x \) gives us the amount of hydrogen that has diffused into the right compartment. Once we have \( x \), we can substitute it back to find the total pressure in the right compartment.

Final Pressures

After performing the calculations, we can summarize the pressures in each compartment:

  • Left compartment (Hydrogen): Approximately 36.945 atm
  • Middle compartment (Oxygen): Approximately 12.315 atm
  • Right compartment (Hydrogen and Nitrogen): Will depend on the value of \( x \) calculated from the equilibrium condition.

This analysis illustrates how gases behave in a confined space and how their pressures can change based on diffusion and the principles of thermodynamics. If you have any further questions or need clarification on any part of this process, feel free to ask!