Answer:
The mass was there all along, it was just in the air. The weight of the oxygen from the air is not weighed in the beginning, only at the end as part of the product, making it seem like there is a total mass change.
Answer:
The total work is 4957.45J
Explanation:
For an ideal gas, at constant temperature the definition of work (W) is

where P is the pressure, V the volume, n the moles number, T the temperature and R the gas constant.
To solve the problem is necessary to replace the two steps in the equation
Stape 1: n = 1 mol, R = 0.082atm.L/K.mol, T = 77ºC = 350K, Pi = 5.50atm and Pf = 2.43atm.

Stape 2: n = 1 mol, R = 0.082atm.L/K.mol, T = 77ºC = 350K, Pi = 2.43atm and Pf = 1.00atm.

The total work is the sum of the two steps

I believe the answer is 11, its been awhile since i was in science
Mole ratios<span> are important because mole ratios allow you change moles of a substance to moles of another substance.</span>