Chemistry MCQ Practice

 

What would be observed for the water level at x after some time?

 

A)  becomes higher

 

B)  becomes lower

 

C)  fluctuates about x

 

D)  remains unchanged

 

 

Answer: B

 

- In this qns, the difficulty comes in that a mixture of gases is present inside the porous pot.

 

- For a mixture of gases, we need to use the average relative molecular mass which will be between that of the 2 gases i.e. between 44 (CO₂) and 71 (Cl₂).

 

- Comparing the values to that of the gas outside the pot: ammonia (relative mass of 17), it is clear that the gas outside the pot will diffuse in faster than the gas inside the pot diffusing out.

 

- After some time, there will be more gas particles inside the pot → pressure is higher → water level at x will become lower.

 

Common mistake: students will put down the relative mass of chlorine to be 35.5. Bear in mind that chlorine exists as a diatomic molecule i.e. Cl₂.