Pre-lab stuff + parts of Sec 3 and 4 notes

At the begining of the lab Dr. B will give us the barometric pressure, but not the units we need, we will have to convert it as part of the lab.
During the lab there will be no chewing on any substances. HCl will be used during the lab and it will burn your skin.
......................................................Missed some info...................................................
Add HCl the the tube then hold the tube with HCl at an angle when squeezing the water slowly into the tube, try not to let the water and HCl mix because it will cause the reaction to go slower. When putting the capper and magnesium in the tube put it in close to the top and not far in the tube. Then you put your finger over the top of the tube and flip it over and into the beaker with water. It should start to bubble and gas will start to form at the what used to be the bottom of the tube, now the top.
NOTES - CH11 sec 3 cont.
The Ideal Gas Law cont.
The Ideal Gas Constant cont.

• The calculated value of R is usually rounded to 0.0821(L x atm)(md x k)
• Dr. B wants Rto equal 0.08206
• use this value in ideal gas law calculations when the volume is in liters, the preasure is in atmospheres, and the temp is in kelvins
• The ideal gas law canbe applied to determine the existing conditions of a gas sample when three of the four values; P,T,V, and n; are known
• be sure to match the units of the known quantities and the units of R
• Sample problem 1: what is the pressure in atmospheres exerted by a 0.500mol smple of nitrogen gas in a 10.0 L container at 298K?........P=nRT/V..........P=(0.500mol)(0.08206L x atm)(298K)/10.0L 122atm

Graham's Law of Efusion

• Rates of effusion and diffusion depend on the relative velocities of gas molecules. the velocity of a gas varies inversely with the square root of its molar mass.
• recall that the average kinetic energy of the molecules in any gas depends on the temperature and equalys(1/2)mv^2
• for 2 different gases, A and B, at the same temperature, the following relationship is true 1/2 MaVa^2= 1/2 MbVb^2
• from the equation relationg the kinetic energy of two different gases at the same conditions, one can derive an equation relating the rates of effusion of two gases with their molecular mass. Rate of effusion of A/rate of effusion of B= square root of Mb/ square root of Ma
• this equation is known as Graham's law of effusion which states that the rates of effusion of gasses at the same temperature and pressure are inversely proportional to the square roots of their molar mass