During one of his adventure Chacha Chaudhary got trapped in an underground cave which was sealed two hundred years back. The air inside was poisonous and contains `CO` in addition to `O_(2)` and `N_(2)`. Sabu, being huge, could not enter cave. In order to save Chacha Chaudhary he started sucking the poisonous air out of the cave by mouth. In each cycle he used to fill his lungs with cave air and exhale it out in the surroundings. In the mean time fresh air `(N_(2)+O_(2))` from the surrounding effused into cave till the pressure was 1 atmosphere. Each time Sabu sucked air,the pressure in the cave dropped ito `1//2 atm`. An initial sample of air taken from the cave measured `11.2mL` at STP and give `7J` on complete combusion at constant pressure.
`(a)` If the safe level of `CO` required in cave for life is less thatn `0.001%` by volume, how many times does Sabu need to suck out air in order to save Chacha Chaudhary ?
`(b)` Sabu should rescue Chacha Chaudhary within 10 minutes else he will die. Precious 80 second are wasted in thinking of a way to rescue him. At maximum how much time should each cycle of inhaling`-`exhaling take. Given, `DeltaH_(comb)CO=-280kJ mol^(-1)` ? Neglect Graham's law effect during operations.

Answer

13