Question

25 points question
Oxygen is present in a 1-litre flask at a pressure of 7.6×10^-10 mm of Hg at 0℃. Calculate the number of oxygen molecules in the flask.
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Answer 1

First we should calculate the number of moles of the gas under the given condition by the relation PV = nRT
Here P = 7.6 × 10-10 mm Hg
= 7.6 × 10^-10/760 atm. = 1 × 10^-12 atm.
V = 1 litre
T = 273 + 0 = 273K
R = 0.082 litre atm./K/mol

Putting the values in equation
n = PV/RT = 1 × 10^-12 × 1/0.082 × 273 moles

Now, since 1 mole = 6.023 × 1023molecules

10^-12/0.082 × 273 moles =
6.023 × 10^23 × 10^-12/0.082 × 273 molecules
= 2.7 × 10^-10 molecules

Hence, no. of molecules present in the 1 litre flask at a pressure of 7.6 × 10^-10 mm Hg at 0°C is 2.7 × 10^-10.

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Answer 2

Heya....✋
Answer is in attachment.....