The following problems are due next week but you should work on them with your g

Question

The following problems are due next week but you should work on them with your group today 3.(15pts) Use the information contained in the following diagrams to compute the pressure of the gas (in atm) for cases (), (ii) and (ii). The atmospheric pressure in each case is 0.960 atm at 2 Open end 5.0°C. The liquid in the manometers is mercury. Closed end Open end Assume evacuated h 18.0 cm h 28.0 cm h 39.0 cm 4.(35pts) The following problems are due next week but you should work on them with your group today. Valves closed He (ideal gas) (Flask on left) V 3.50 L P 412 torr Ne (ideal gas) (Flask in middle) V = 7.00 L P = 237 torr Ne (ideal gas) (Flask on right V- 3.00 L 667 torr When the valves are open, the gases will mix. Assuming that the temperature is constant, what is the final total pressure in torr? Hint: First compute the partial pressures of each gas after it expands to fill entire space after the valves are open. the Bonus Problem (+6nts No partial credit A S00 0 ma table ofan antacid containing MOLD AKOH

Explanation / Answer

Solution:- (3)(i) In the first picture, gas is connected to one of the end of the u-tube of manometer and other end is closed. The mercury level is high in the closed end. For this, the gas pressure equals to the difference of mercury level in two ends.

Pgas = Ph

Pgas = 18.0 cmHg

Let's convert this to atm as....

18.0 cmHg x (10 mm/1cm) x (1 atm/760 mm mmHg) = 0.237 atm

(ii) In second diagram, the othe end is open and the mercury level is high in the tube connected to the gas. It means the atmospheric pressure is greater than gas pressure and this is equal to the mercury level difference of two ends.

Pgas + Ph = Patm

Pgas + 28.0 cmHg = 0.960 atm

Pgas = 0.960 atm - 28.0 cmHg

Need to convert 28.0 cmHg to atm.

28.0 cmHg x (10 mm/1cm) x (1 atm/760 mm mmHg) = 0.368 atm

So, Pgas = 0.960 atm - 0.368 atm = 0.592 atm

(iii) For the third diagram the mercury level is high in the open end tube it means the gas pressure is greater than atmospheric pressure.

Pgas = Patm + Ph

Pgas = 0.960 atm + 39.0 cmHg

Let's convert 39.0 cmHg to atm..

39.0 cmHg x (10 mm/1cm) x (1 atm/760 mm mmHg) = 0.513 atm

Pgas = 0.960 atm + 0.513 atm = 1.473 atm

(4) Initial pressure of He, P1 = 412 torr

initial volume, V1 = 3.50 L

When the Valves are open then total volume = 3.50 L + 7.00 L + 3.00 L = 13.50 L

So, Final volume for He, V2 = 13.50 L

Final pressure of He which is also it's partial pressure, P2 = ?

temperature is constant, So, from Boyle's law, P1V1 = P2V2

P2 = P1V1/V2  

P2 = 412 torr x 3.50 L/13.50 L = 106.8 torr

Similarly for second flask, Patial pressure of Ne, P2 = 237 torr x 7.00 L/13.50 L = 122.9 torr

And, for third flask ,the partial pressure of Ne, P2 = 667 torr x 3.00 L/13.50 L = 148.2 torr

From dalton's law of partial pressure, total pressure is the sum of partial pressures of all the gases present in the flask.

So, total pressure, Ptotal = 106.8 torr + 122.9 torr + 148.2 torr = 377.9 torr or almost 378 torr

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