Kinetic Molecular Theory and Real Gases ROOT MEAN SQUARED, EFFUSION, REAL GASES

Visit: Log in and select Chem 1A. When prompted, type the word of the day: kmt Ensure when asked if you will share your location you select “allow”. Visit: Sign in MasteringChemistry account name When prompted, type session ID: Please turn off all downloads. You can usually pause them by clicking on them and clicking pause. Facebook and youtube are officially banned during class time (this is not me micromanaging, it’s a legit internet issue as told to me by OIT). Remember back 5 rows of even side are no seating zones Visit: Word of the day: kmt LearningCatalytics: session ID:

ANNOUNCEMENTS I still don’t have midterm 3 back, it’ll be up as soon as I have them. Figure out grade using midterms and assume as long as you show up most classes and do most of the homework it’ll balance out. (you get to drop enough that generally it shifts the curve up for everyone) Please remember to do my evals, they’ll stop sending you annoying s. Remember to put things you like as well as things you don’t like so I don’t change things most people like due to the vocal few. Homework for chapter 11 are shorter assignments, there are just three of them because of how the chapter breaks up. Office Hours next week. Monday 10-11:30, and Monday 2-3, Tuesday 3-4. Exam is Wednesday 8-10 please show up on time and in seats! Extra credit is due day of the final exam, printed please. Remember back 5 rows of even side are no seating zones Visit: Word of the day: kmt LearningCatalytics: session ID:

SURVEY QUESTIONS Visit: Word of the day: kmt LearningCatalytics: session ID:

SURVEY QUESTIONS: TEMPERATURE ISSUES For the RMSspeed equation, do we always use 298K when we are not given a temperature value? You should always be given it or a way to calculate it. Otherwise ask. STP is 0 o C, aka 273 K If given two temp in o C and asked for final volume do we need to convert celsius to kelvin Yes, always always always always convert into Kelvin when dealing with temperatures in this unit. Low temp,= slower moving Either, less pressure, or less volume High temp= faster moving Either, higher pressure, or higher volume Why does temperature make volume bigger? Pressure changes if rigid container Volume changes if non rigid container/movable piston ect….. Visit: Word of the day: kmt LearningCatalytics: session ID:

QUIZ QUESTION 1 Which is true according to the kinetic molecular theory? Molecules are point masses Collisions are elastic Gas molecules are attracted to each other Gas molecules repel each other Gas molecules are neither attracted nor repulsed Gas molecules in a sample are all traveling at the same speed Visit: Word of the day: kmt LearningCatalytics: session ID:

KINETIC MOLECULAR THEORY OF GAS What is Kinetic energy? Energy of motion Kinetic theory of gases Assume molecules are point masses (possess mass but no volume) Constant random motion, collisions are completely elastic energy can be transferred, but total energy remains the same. Gas molecules are neither attracted or repulsed Visit: Word of the day: kmt LearningCatalytics: session ID:

KINETIC MOLECULAR THEORY: PRESSURE Pressure is created by collisions between molecules and the container. Visit: Word of the day: kmt LearningCatalytics: session ID:

DISCUSSION QUESTIONS: KINETIC MOLECULAR THEORY Do all your molecules hit the walls of their container with the same force? Justify your answer based on kinetic molecular theory. No: Not all molecules are traveling at the same speed, since force increases as velocity increases, a molecule traveling faster will hit with more force. Visit: Word of the day: kmt LearningCatalytics: session ID:

Which of the two lines represents the sample at a higher temperature? Higher temp= faster rms T 2 = faster rms= higher temperature Visit: Word of the day: kmt LearningCatalytics: session ID:

Which of the two lines represents with a higher molecular mass? M1M1 M2M2 Smaller mass = faster rms M 1 = slower rms= heavier Visit: Word of the day: kmt LearningCatalytics: session ID:

DISCUSSION QUESTIONS: KINETIC MOLECULAR THEORY How does the frequency and force (respectively) of the collisions of the molecules of a gas with the walls of the container change as the temperature of the gas is decreased? Justify based on kinetic model of gases. Decrease, Decrease The distribution of speeds is lowered as the temperature is lowered, so the molecules will hit the walls less often due to slower movement, and will also hit with less force due to slower movement. Visit: Word of the day: kmt LearningCatalytics: session ID:

DISCUSSION QUESTIONS KINETIC MOLECULAR THEORY If you increase the molecular mass, the rms ____________. Justify your answer A) IncreasesB) DecreasesC) stays the same Decreases The rms speed is as shown in the formula below. Therefore it is inversely related to molecular mass. The more mass a molecule has, the slower it will go. Visit: Word of the day: kmt LearningCatalytics: session ID:

Calculate the rms speed of an oxygen gas molecule, O 2, at 29.0 ∘ C. Visit: Word of the day: kmt LearningCatalytics: session ID:

Explain how each of the below laws follow from kinetic molecular theory. Boyle's law, (P&V): Charles's law(V&T)/Gay-Lussac’s(P, T), Avogadro's law, (n&V or P) and Dalton's law (partial pressures) P1V1=P2V2 If the pressure is decreased, the force on the walls must be decreased. This happens by decreasing the frequency of collisions by increasing the size of the container. P1/T1=P2/T2 If the temperature is increased the force on the walls will increase as well. This is from both increased number and increased speed of collision. This increases the pressure. V1/n1=V2/n2 If the number of moles is increased the number of collisions with the wall will increase, therefore increasing the volume. Pa+Pb+Pc…..=Ptotal and that PV=(na+nb+nc…)RT Because all the molecules will hit the wall with the same force (faster molecules are lighter at the same temperature), Visit: Word of the day: kmt LearningCatalytics: session ID: