To determine the composition of hydrogen gas (H2) in flask B after the valve is opened, we need to analyze the situation using the ideal gas law and the concept of partial pressures. Let's break it down step by step.

Initial Conditions

We have two flasks:

• Flask A: Volume = 10 liters, H2 = 20 grams
• Flask B: Volume = 10 liters, CO2 = 88 grams

Calculating Moles of Gases

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

• Molar mass of H2 = 2 g/mol
• Molar mass of CO2 = 44 g/mol

Now, let's calculate the number of moles:

• Moles of H2 in Flask A = 20 g / 2 g/mol = 10 moles
• Moles of CO2 in Flask B = 88 g / 44 g/mol = 2 moles

Calculating Total Moles After Opening the Valve

When the valve is opened, the gases will mix, and we need to find the total number of moles in the combined volume of both flasks:

• Total moles = Moles of H2 + Moles of CO2 = 10 moles + 2 moles = 12 moles

Finding the Composition of H2 in Flask B

Next, we need to find the partial pressure of H2 in the total volume after mixing. The total volume is the sum of the volumes of both flasks, which is 20 liters.

Calculating the Mole Fraction of H2

The mole fraction of H2 can be calculated as follows:

• Mole fraction of H2 = Moles of H2 / Total moles = 10 moles / 12 moles = 5/6

Calculating the Composition in Flask B

Now, we need to find out how much of this H2 will be present in Flask B, which has a volume of 10 liters. Since the gases distribute evenly, we can use the mole fraction to find the amount of H2 in Flask B:

• Moles of H2 in Flask B = Mole fraction of H2 × Total moles in Flask B
• Since Flask B has a total of 2 moles of gas (2 moles of CO2), the moles of H2 in Flask B = (5/6) × 2 moles = 10/6 = 1.67 moles

Calculating the Total Moles in Flask B

Flask B initially had 2 moles of CO2. After mixing, the total moles in Flask B become:

• Total moles in Flask B = Moles of CO2 + Moles of H2 = 2 moles + 1.67 moles = 3.67 moles

Final Composition of H2 in Flask B

To find the composition of H2 in Flask B as a percentage, we use the formula:

• Composition of H2 = (Moles of H2 in Flask B / Total moles in Flask B) × 100
• Composition of H2 = (1.67 moles / 3.67 moles) × 100 ≈ 45.5%

However, since we are interested in the percentage of H2 relative to the total gas mixture in Flask B, we can also express it as:

• Percentage of H2 = (Moles of H2 in Flask B / (Moles of H2 in Flask B + Moles of CO2 in Flask B)) × 100
• Percentage of H2 = (1.67 / (1.67 + 2)) × 100 ≈ 45.5%

Given the options provided (A) 10%, (B) 13%, (C) 15%, (D) 20%, it seems there might be a misunderstanding in the calculation or the options provided, as the calculated percentage of H2 in Flask B is significantly higher than any of the given choices. Please double-check the values or the context of the question.