Someone help me with these questions about Italy?

Gas Laws questions?? Someone please help?

• Okay I have a final exam on Friday and I need help with both understanding and solving these problems so can someone please help me because I truly am trying to understand how to address and arrive to an answer for these questions. 1) a scuba diver's tank contains 0.29kg of O2 compressed into a volume of 2.3L. a)Calculate the gas pressure inside the tank at 9 degrees Celsius A was already solved but b is where I am confused. b)what volume would this oxygen occupy at 26 degrees Celsius and 0.95 atm?? I did the calculations but the answer was wrong and I'm not sure why exactly I am just given an answer not an explanation so can someone please help me the answer for 2b was 2.3*10^2L. But can you explain the steps to the answer I used PV=nRT but the answer was wrong, was that the incorrect formula to use?? 2) a: Calculate the density of NO2 gas at 0.907 atm and 35 degrees Celsius. b) Calculate the molar mass of a gas if 2.05g occupies 0.875L at 685 torr and 35 degrees Celsius. For the second problem I don't know how to address them at all so can someone please help explain the steps on how to solve this problem I would truly appreciate it and I thank you very much in advance :)

• Answer:

  First solve for pressure for 1a PV=nRT n= 0.29 x 1000/32 (need to convert kg to g) and then divide by 32 to get mols of O2 R = 0.0821 T= (9C +273.15K) need to convert C to kelvin P= unknown If you plug in and computer solving for P you will get 91.24 atms For part 2 just use PV=nRT again P=0.95 n=9.06 (from previous problem) R = 0.0821 T=(26+273.15) V= uknown Plug in and compute and you get 234 but I'm guessing they want 2 sig figs so it will be 2.3x10^2 ======================================… For the second question you were using the wrong formula. You have to use d = PM/(RT) d= density P=pressure in atms M=molecular weight in grams R=0.0821 T= temperature in kelvin You get the hang of it now so I'll compress the calculation. d=(.907)(46g)/(0.0821)(35+273.15) solve and you should get 1.64g/L ======================================… Finally for part 2b you should use PV=nRT again solving for n first. Don't forget to convert 685 torr to atms. 760 torr in 1 atm so 685/760 = .9 atms (0.9)(0.875L)/(0.0821)(35+273.15) = .03 mols Molar mass is g/mol so just divide 2.05 grams by .03 and you should get 68.34 grams/mol ======================================… DONE!!!!