Consider the flask apparatus below, which contains 2.00 L of H2 at a pressure of 353 torr and 1.00 L of N2 at an unknown pressure. A flask apparatus is composed of two round flasks connected by a single tube fitted with a closed stopcock. The flask on the left has a volume of 2.00 L and contains H2. The flask on the right has a volume of 1.00 L and contains N2. If the total pressure in the flasks is 373 torr after the stopcock is opened, determine the initial pressure of N2 in the 1.00 L flask. (Assume the final volume is 3.00 L.)

Initial pressure of N2 was 413 torr

Explanation:

Given:

- Initial Pressure of H2 = 353 torr

- Initial Volume of H2 = 2 L

- Final Volume of H2 = 3 L

- Total pressure at end = 373 torr

- Iinitial Volume of N2 = 1 L

- Final Volume of N2 = 3 L

Find:

determine the initial pressure of N2 in the 1.00 L flask.

Solution:

- Lets focus on the H2 at first, from pascal's Law we have:

                                P_1 x V_1 = P_2 x V_2

                                   (353)(2) = (P)(3)

                             P = 353*2 / 3 = 235.333 torr

- Since the total pressure remains constant the Pressure P of the N2 at the end would be

                              373 - 235.33 = 137.667 torr

- Now calculate the original P of N2  , again using Pascal's Law:

                                     (P)(1) = (137.667)(3)

                                   P = 137.667*3 = 413 torr

Initial pressure of N2 was 413 torr