Learning log
Chapter 11 pressure of gases
This week of chemistry started with learing about pressure. Pressure has an inverse relationship with surface area as well as elevation. It also has a direct relationship with tempature. By inverse one means that when one thing increases the other decreases. Using pressure and suface area as an example is how people lay on a bed of nails. This works becuse with more more nails one can lay all ones, weight with not much pressue because there is a large surface area (Less pressure more surface area). A direct relationship means one increases and the other increases. An example of this would be if if on a hot day a ballon popped because the pressure increase as it became warmer (Greater pressure hotter tempature). you can measure atmospheric (atm) or outside pressure using a barometer. The earliest barometer mesure mm Hg because how one had measured the atm mecury inside a graduated tube in a pool of mecury upside down and when the perssure inside the tube leveled with the atmospheric pressure it would stop pushing down on the mecury inside the tube and was measured in mm (ie mm Hg). There have been many different ways of measuring pressure however atm is the baisline with everything eles equaling 1 atm. Some of these include 760 torr, 760 mmHg,1.01325 Pa (pascel), 101.325 kPa, and 14.700psi. Using these numbers one can easily convert different units of pressure to find other units. When masuing tempature it is often told in celcius however when meausing pressure one uses kelvin. To convert celcius to clevin add 273 degrees. There are three law for finding tempature pressure or volume for a gass. These are Boyles Law P_1+V_1= P_2+V_2 to solve for pressure with volume or vice versa, then there is Charles's Law V_1/T_1= V_2/T_2 to solve for voulume with tempature vice versa, and Gay-Lussac's law P_1/T_1=P_2/T_2 to solve for pressure to tempature or tempature from pressure. There is then the Combined Gas Law are all the previous laws P_1V_1/ T_1= P_2T_2/T_2. There is a standard tempature and pressure (STP) is 1 atm and 0'C. There is also the ideal gas law which measures how much a certain gas takes up at a pressure. The formula for this is PV=nRT where n is the number of moles and R is the ideal gass constaint (0.0821 atm/mol K). If oyu are given a problem such as What is the pressure in atm exerted by a .500mol sample of N_2 gas in a 10.0L container at 298K. RThis problem would be carried out by P(10.0L)= (.500mol)(.0821atm/mol K . One then solves for P which would equal 1.22 atm. Lastly, one can slove for how many L make how many moles. There is about 22.4 L in one mole so doing simple multiplication or division one can solve for L or moles. An example of this is .0685mol to how many L would be .0685* 22.4= 1.54L.