EXAM 1 Constants: Thermodynamics, Summaries of Thermodynamics

Download EXAM 1 Constants: Thermodynamics and more Summaries Thermodynamics in PDF only on Docsity! Physics 2020 Spring 2009 Stephan LeBohec COVER SHEET - EXAM 1 Constants: k=1.38×10−23 J⋅K−1 R=8.31 J⋅mol−1⋅K −1 N A=6.02×1023 Thermodynamics: T K =T C 273 P⋅V =N⋅k⋅T =n⋅R⋅T First law of thermodynamics: U=Q−W n= N N A = m M &  R=N A⋅k Ideal mono­atomic gas: U=3 2 n⋅R⋅T Isochoric: W =0 Isobaric: W =P V f −V i Isothermal W =n⋅R⋅T ln  V f V i  Adiabatic: W =−3 2 n⋅RT f−T i & P⋅V =Constant with = 5 3 for mono­atomic gases e Actual= W Cycle Q H =1− QC QH eCarnot=1− T C T H Waves: =c⋅T = c f as  f = 1 T cString= F  with =m L In a gas cSound= P  with  = 5 3 for a mono­atomic ideal gas Isotropic sound intensity: I= P 4⋅r 2 Comparing intensities =10 log10 I 1 I 2 in dB Doppler effect:  f o= f s c±vo c∓vs SEAT # A. A 10−3 m3 flask contains one gram of H 2 ( 2g⋅mol−1 ) and one gram of O2 ( 32g⋅mol−1 ) gas in thermal equilibrium. For each statement, circle the option you find appropriate. You do not need to show your work. 1. [2 points] Each gas exerts an equal pressure. TRUE or FALSE ? Because PO V =nO R T & PH V =nH R T so PH /PO=nH /nO . 2. [2 points] The root mean square (RMS) velocity of H 2 molecules is the same as the RMS velocity of O2 molecules. TRUE or FALSE ? Because 3 2 k T=1 2 mO v RMSO 2 = 1 2 mH vRMS H 2 so vRMS O ≠v RMSH 3. [2 points] The average energy of an H 2 molecule is the same as the average energy of an O2 molecule. TRUE or FALSE ? Because 3 2 k T=1 2 mO v RMSO 2 = 1 2 mH vRMS H 2 4. [3 points] The RMS velocity of H 2 molecules is greater than the RMS velocity of O2 molecules by a factor of 1, 4, 16 or 256 ? 3 2 k T=1 2 mO v RMSO 2 =1 2 mH vRMS H 2 so vRMS H /v RMS O =mO /mH= 32/2=4 5. [2 points] If the average temperature of the mixture is T , the average temperature of one species of molecules is greater than T and the average temperature of the other species is less than T . TRUE or FALSE ? The system is in thermal equilibrium, all its parts are at the same temperature. 6. [3 points] When the temperature is doubled, the RMS velocities of both species of molecules are multiplied by a factor of 1, 2 , 2 or 4 3 2 k T= 1 2 m v2 so v=3kT /m , when the temperature doubles the RMS velocity is multiplied by 2 7. [2 points] When the temperature of the mixture is increased the amount of work done by the gas is NEGATIVE, ZERO, or POSITIVE V =0 so no work is done 8. [2 points] It is possible to change the temperature of the gas in the flask via an adiabatic process. TRUE or FALSE ? Adiabatic implies Q=0 and we also have W =0 , so U=0 and T=0 Physics 2020 Spring 2009 Stephan LeBohec EXAM 1 Name:_____________________________________ Student ID #:___________________________ TA (circle one): Michael Sarah Adam Isaac 1