The diagram shows two flasks X and Y connected by a thin tube of negligible volume - AQA - A-Level Physics - Question 8 - 2020 - Paper 2

To find the mass of gas in flask Y, we can use the concept of the ideal gas law, which states that for an ideal gas, the ratio of mass to temperature is constant, provided the volume ratio is known.

1. Let the volume of flask Y be V. Therefore, the volume of flask X is 2V.

2. The temperatures are given as follows:

   • Temperature of X, T_X = 100 K
   • Temperature of Y, T_Y = 400 K

3. The ratio of the number of moles of gas in each flask, under constant conditions, corresponds to the mass and temperature, which gives us:

   ( \frac{m_X}{T_X} = \frac{m_Y}{T_Y} )

   This means: [ m_Y = m_X \cdot \frac{T_Y}{T_X} \cdot \frac{V_Y}{V_X} ]

4. Since ( m_X = m ), the mass of gas in Y can be expressed as: [ m_Y = m \cdot \frac{400}{100} \cdot \frac{V}{2V} ]

5. Simplifying this: [ m_Y = m \cdot 4 \cdot \frac{1}{2} = 2m ]

Thus, the mass of gas in Y is ( 2m ), corresponding to option B.