you would change one element to a diffrent element
Answer: The correct option is (c). The total pressure doubles.
Solution:
Initially, only 4 moles of oxygen gas were present in the flask.
(
) ( according to Dalton's law of partial pressure)
....(1)
= Total pressure when only oxygen gas was present.
Final total pressure when 4 moles of helium gas were added:

partial pressure of oxygen in the mixture :
Since, the number of moles of oxygen remains the same, the partial pressure of oxygen will also remain the same in the mixture.

= Total pressure of the mixture.
from (1)

On rearranging, we get:

The new total pressure will be twice of initial total pressure.
True. A gas does not have a definite volume. Therefore, making this statement correct. <span />
Answer:
Explanation:
Well the gas is the fuel for the flame of course. The collision theory comes into play when the gas turns on, chemicals collide with one another. Then reactions occur causing the flame. Then when you take away the fuel, the flame stops because there is no atoms or molecules to come together/collide with one another.
Sorry if its wrong or doesn't make sense... Wish you the best of luck on whatever your doing!