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Current Question (ID: 19852)

Question:
$\text{Same gas is filled in two vessels of the same volume at the same temperature. If the ratio of the number of molecules is } 1 : 4, \text{ then:}$
Options:
  • 1. $\text{(A) The RMS velocity of gas molecules in two vessels will be the same.}$
  • 2. $\text{(B) The ratio of pressure in these vessels will be } 1 : 4$
  • 3. $\text{(C) The ratio of pressure will be } 1 : 1$
  • 4. $\text{(D) The RMS velocity of gas molecules in two vessels will be in the ratio of } 1 : 4$
Solution:
$\text{Hint: } V_{\text{rms}} = \sqrt{\frac{3kT}{m}}$ $\text{Step 1: Find the correct ratio of the pressures.}$ $\text{Let } P_1, N_1 \text{ be the pressure and the number of molecules of the gas in the first vessel, and } P_2, N_2 \text{ be the pressure and the number of molecules of the gas in the second vessel.}$ $\text{Given the ratio of the number of molecules;} \Rightarrow \frac{N_1}{N_2} = \frac{1}{4} \Rightarrow N_2 = 4N_1$ $\text{The ideal gas law states that;} PV = NkT \quad \ldots (1)$ $\text{where } P \text{ is the absolute pressure of a gas, } V \text{ is the volume it occupies,}$ $N \text{ is the number of atoms and molecules in the gas, and } T \text{ is its absolute temperature,}$ $k \text{ is the Boltzmann constant.}$ $\text{Using (1), the ratio of the pressures is given by;}$ $\Rightarrow \frac{P_1V}{P_2V} = \frac{N_1kT}{N_2kT} \Rightarrow \frac{P_1}{P_2} = \frac{N_1}{N_2} = \frac{1}{4}$ $\text{Step 2: Find the correct ratio of the } V_{\text{rms}}.$ $\text{Let } V_1, V_2 \text{ be the RMS velocity of the gas in the first and the second vessel.}$ $\text{For an ideal gas, the RMS velocity is given by;}$ $V_{\text{rms}} = \sqrt{\frac{3kT}{m}} \quad \ldots (2)$ $\text{where } T \text{ is its absolute temperature, } k \text{ is the Boltzmann constant and } m \text{ the mass of one gas molecule.}$ $\text{Using (2), the ratio of the } V_{\text{rms}} \text{ is given by;}$ $\Rightarrow \frac{V_1}{V_2} = \frac{\sqrt{\frac{3kT}{m}}}{\sqrt{\frac{3kT}{m}}} = \frac{1}{1}$ $\text{Therefore, (A) and (B) are the valid statements.}$ $\text{Hence, option (3) is the correct answer.}$

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Expected JSON Format:

{
  "question": "The mass of carbon present in 0.5 mole of $\\mathrm{K}_4[\\mathrm{Fe(CN)}_6]$ is:",
  "options": [
    {
      "id": 1,
      "text": "1.8 g"
    },
    {
      "id": 2,
      "text": "18 g"
    },
    {
      "id": 3,
      "text": "3.6 g"
    },
    {
      "id": 4,
      "text": "36 g"
    }
  ],
  "solution": "\\begin{align}\n&\\text{Hint: Mole concept}\\\\\n&1 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\text{ moles of carbon atom}\\\\\n&0.5 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\times 0.5 \\text{ mol} = 3 \\text{ mol}\\\\\n&1 \\text{ mol of carbon} = 12 \\text{ g}\\\\\n&3 \\text{ mol carbon} = 12 \\times 3 = 36 \\text{ g}\\\\\n&\\text{Hence, 36 g mass of carbon present in 0.5 mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6].\n\\end{align}",
  "correct_answer": 4
}