[Damuffinator]

Me and my friend can't seem to figure out how to solve these two questions. Our textbook is next to useless and our prof has the significance of a toaster.

Here are the two questions:


1. When two grams of a gaseous substance A is introduced into an initially evacuated flask maintained at a constant temperature T, the pressure is found to be one bar.  When three grams of a second gaseous substance B is added at the same temperature to the two grams of A, the pressure increases to 1.5 bar.  Calculate the ratio of the molar mass of B to that of A.


2. A polyethylene bag is filled with air at one atm pressure and taken underwater to provide oxygen for breathing.  Oxygen becomes toxic to humans when its partial pressure reaches about 0.8 atm.  At what depth will breathing that air from this bag lead to oxygen toxicity?


Any help for these questions would be greatly appreciated, we've been stuck on them for a while, thanks!

[Borek]

1. When two grams of a gaseous substance A is introduced into an initially evacuated flask maintained at a constant temperature T, the pressure is found to be one bar.  When three grams of a second gaseous substance B is added at the same temperature to the two grams of A, the pressure increases to 1.5 bar.  Calculate the ratio of the molar mass of B to that of A.

Calculate partial pressures. They are proportional to the number of moles of substance. Knowing ratio of numbers of moles and masses you should be able to calculate ratio of molar masses.

2. A polyethylene bag is filled with air at one atm pressure and taken underwater to provide oxygen for breathing.  Oxygen becomes toxic to humans when its partial pressure reaches about 0.8 atm.  At what depth will breathing that air from this bag lead to oxygen toxicity?

How much oxygen in the air? How does the partial pressure depend on the total pressure? How does the total pressure depend on the depth?

[Damuffinator]

Ah we got it! Thanks very much! We've managed to get ourselves stuck on another question though, mind giving us another hand? We've been stuck on this one for a while and we're not entirely sure how to solve it.

Calculate the work required to exclude one atmosphere from one cubic centimetre, using the information that one atmosphere is just balanced by a column of mercury of 760mm in height and that the density of the mercury is 13.5955 g cm-3. The acceleration due to gravity is 9.80665 m s-2.

Thanks so much! Very much appreciated

[Borek]

W=FS

[animal123]

good luck with your u of t, 1st year engineering phys chem mid term today!