ENV6666_MOD4_text_1 - ENV 6666 AQUATIC CHEMISTRY Professor...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ENV 6666 AQUATIC CHEMISTRY Professor: Dr. Maya Trotz Module 4 Gas/Liquid Equilibrium and Open Systems © 2010 University of South Florida: Dr. Maya Trotz & Mr. Arlin Briley Page 1 of 34 Contents © 2010 University of South Florida: Dr. Maya Trotz & Mr. Arlin Briley Page 2 of 34 Partial Pressure of a Gas The Ideal Gas Law should be familiar to any student of chemistry. It may be written = PV nRT where • P = pressure exerted on the gas (which is equal to the pressure exerted by the gas) • V = volume occupied by the gas • n = number of moles of gas atoms or molecules (as appropriate) • R = the universal gas constant • T = the temperature in Kelvin In this class we will typically assume room temperature, so it is handy to lump RT together in one of the following forms, depending on the units used: RT 25°C = 592.5 cal/mol = 2479 J/mol = 24.47 (L∙atm)/mol = 24.79 (L∙bar)/mol There are expressions for RT in other units, but only the most commonly used are listed here. Air in our atmosphere is approximately 76% nitrogen, 20% oxygen, 0.9% argon, 0.0385% carbon dioxide, varying amounts of water vapor (a few percent), and trace amounts of other gases such as neon, helium, ozone, etc. Air is thus a mixture of gases, each gas made up of particles (atoms for gases such as neon or helium; molecules for gases such as nitrogen, oxygen, or carbon dioxide, which are N 2 , O 2 , and CO 2 , respectively). In a container of air there would be some total number of gas particles, but because they are so small, we use units of moles (one mole of gas particles is . × 6 02 1023 particles). If we could count the moles of each gas separately, they would add up to some total, so we could write: = + + + +… ntotal nN2 nO2 nCO2 nAr If we imagine that each gas species could be separated by type and put into individual balloons, so that all the nitrogen is in one balloon, all the oxygen in another, all the carbon dioxide in another, etc., but the overall pressure within the container stays the same, then the total volume would be the sum of the individual volumes: = = + + +… Vcontainer Vair VN2 VO2 VCO2 In each balloon the Ideal Gas Law would apply, and the pressure would be the same for all balloons, so the Ideal Gas Law would give (using nitrogen as an example): = PVN2 nN2RT (or, rearranging) = VN2 nN2RTP Substituting into the sum of volumes relationship, we would get: = + + +… Vair nN2RTP nO2RTP nCO2RTP In real life, however, the gases are not separated, and are so thoroughly mixed that there is nitrogen in all parts of the container, oxygen in all parts, and so on. In other words, it is more realistic to consider that each species of gas occupies the entire volume of the container, subject to the overall pressure. With this idea in mind, multiply both sides of the equation by P and divide by Vair to find: © 2010 University of South Florida: Dr. Maya Trotz & Mr. Arlin Briley Page 3 of 34 = + + +… P nN2RTVair nO2RTVair nCO2RTVair This says that the total pressure of the container of air is the sum of contributions from each species of gas...
View Full Document

{[ snackBarMessage ]}

Page1 / 34

ENV6666_MOD4_text_1 - ENV 6666 AQUATIC CHEMISTRY Professor...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online