Answer:
Total pressure in atmosphere IS 4.36 atm
Explanation:
Given Data:
Depth of lake is 400 mtr
surface tension is 147 kilopascals
surface temperature 94 kelvin
Gravity = 1.35 m/s^2
specific gravity of methane(liquid) = 0.415
specific gravity of ethane(liquid) = 0.546
density of methane can be obtained as

Density of ethane can be obtained as

Total pressure in atmosphere can be obtained as


= 441.84 kPa

= 4.36 atm
Decreases, stays the same, increases.
The volume decreases because as air is cooled, the individual molecules collectively possess less kinetic energy and the distances between them decrease, thus leading to a decrease in the volume they occupy at a certain pressure (please note that my answer only holds under constant pressure; air, as a gas, doesn't actually have a definite volume).
The mass stays the same because physical processes do not create or destroy matter. The law of conservation of mass is obeyed. You're only cooling the air, not adding more air molecules.
The density decreases because as the volume decreases and mass stays the same, you have the same mass occupying a smaller volume. Density is mass divided by volume, so as mass is held constant and volume decreases, density increases.
The work is 90 as 5 times 18