# PCHEM Workshop 9 Notes

Updated: Dec 30, 2019

*Ninth workshop with Dineli for **Physical Chemistry (CHEM 3321) with Dr. Nielsen** at UT Dallas!*

**To anyone reviewing my notes: **Please feel free to reach out if you need any clarification on anything I wrote — it might be a moment for me to get back to you, but I’m more responsive now! 🙂 Finally catching up with everything.

**If you want to contact me **for more information/ any clarification/ to start a study group/ need talk to someone…** please comment below, DM me on ****Instagram****, or send an email **by clicking this link, the icon in the top right corner, or manually typing out breealbright@gmail.com.

**WORKSHOP WITH DINELI** | November 5, 2019

Be sure to check Dineli’s page for her notes online. These are not the **complete** answers for the problem set. Make sure you plug and chug to get the individual answers! Also, verify any answers shown here — Dineli always stresses that we should verify the calculations from workshop!

**Problem 1**
A gaseous compound is placed in a rigid container of volume 10.0 L at temperature 300.0 K and at pressure 1.0 atm. The container is placed in an evacuated chamber and a small hole of area 2.65 mm2 is made in one of the container walls. It takes 1.00 minutes for the gas pressure in the container to fall to half of its original value. Determine the molar mass of the gas.

**Problem 2 **
100.0 g of liquid copper (molar mass 63.546 g/mol; melting point 1358 K; density 8.02 g/mL) is placed in a rigid container of volume 10.0 L at temperature 1508 K. The container is placed in an evacuated chamber and a small hole of area 3.23 mm2 is made in the upper container wall. After 2.00 hours, the mass of copper in the container has decreased by 0.0168 g. Assuming the mass loss is due to effusion, calculate the vapor pressure of liquid copper at 1508 K. Hint: because the liquid constantly evaporates, the pressure inside the container is constant.

**Problem 3 **
Interstellar space has an average temperature of about 10 K and an average density of hydrogen atoms of about one hydrogen atom per cubic meter. Compute the mean free path of hydrogen atoms in interstellar space. Assume the diameter of a hydrogen atom to be 100 pm.

**Problem 4 **
On average what is the time between collisions of a xenon atom at 300 K and (a) one torr pressure; (b) one bar pressure.

**Problem 5**
A space vehicle of internal volume 3.0 m3 is struck by a meteor and a hole of radius 0.1 mm is formed. (a) If the oxygen pressure within the vehicle is initially 100 kPa, how long will it take to fall to 20 kPa? (b) Repeat the calculation using nitrogen as the gas. 1

**Problem 6 **
In a double glazed window the panes of glass are separated by 5.0 cm. What is the rate of transfer of heat by conduction from the warm room (25 ◦C) to the cold exterior (-10 ◦C) through a window of area 1.0 m2 ? What power heater is needed to made up of the heat loss? (you may assume nitrogen at 1 atm is between the plates at a temperature midway between the cold and the warm pane of glass)

**Problem 7 **
Calculate the diffusion constant of argon at 25 ◦C and (a) 100 kPa; (b) at 1.00 Pa. (c) If a pressure gradient of 0.10 atm/cm is established in a pipe, what is the flow of the gas due to diffusion?

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