Cheatography

# Chapter 9 - Gases Cheat Sheet by mjb

chem200 gases cheat sheet to use when studying

### Gas Laws

 Boyle's Law PinitialVinitial=PfinalVfinal Charles's Law Vi÷Ti = Vf÷Tf Combined Gas Law PiVi÷Ti = PfVf÷Tf Avogadro's Law Vi÷ni=Vf÷nf Ideal Gas Law PV=nRT Dalton's Law of Partial Pressure Ptotal=P1+P2+P3...

### Dalton's Law of Partial Pressure

 Partial Pressure Pgas(atm)=­(total pressure x molesgas)÷total moles PP when volumes are different Ptotal=P1(atmxV1÷Vtotal)+P2(atmxV2÷Vtotal)... Mole fraction moles of gas ÷ total moles Wet Gas Pwet gas=Ptotal-PH2O then use PV=nRT to solve for variables

### Real Gases

 Van der waal's equation P=[(nR­T)÷­(V-nb)] - [(a*n2)÷(V2)] When comparing real gases a gas with a larger "­a" value will require the largest correction to account for interm­ole­cular forces a gas with a smaller "­b" value will behave most ideally at high pressures If Vdw's pressure is lower than the ideal pressure, attractive forces dominate If Vdw's pressure is higher than ideal pressure, repulsive forces dominate Real Gas Behavior attractive forces between molecules cause a decrease in pressure As molecules increase in size deviations from ideal behavior become apparent at relatively HIGH temps In general, most gases behave most ideally at HIGH temps and LOW pressures

### Pressure Units and Conver­sions

 1 atm= 1 atm (R= .08206) 760 mmHg (R= 62.364) 760 torr 1.013x105 Pa 101.3 kPa 29.92 inches Hg 14.69 psi 1.01325 bar

### Stoich­iometry and Gases

 Mole ratio = Volume ratio 2A+3B=AB 2A:3B 2mL A:3mL B

### Kinetic Molecular Theory

 Temper­ature If temper­ature is increased, Pressure and KE increase by a factor of Tf÷Ti and rms increases by a factor of √Tf÷Ti Volume If volume is increased, Pressure increases by a factor of Vi÷Vf while KE and rms increase by a factor of 1 (because they are not affected)) Moles If moles are increased, pressure increases by a factor of nf÷ni, while KE and rms increase by a factor of 1 (no change)

### Using Ideal Gas Law to Calculate Gas Properties

 Ideal Gas Law PV=nRT STP 0 degrees celcius, 273 degrees Kelvin, 1 atm, 22.4 L/mol Density d=MP÷RT where M is molar mass Volume When not given volume, but told to assume ideal gas behavior, use V=1L

### Diffusion and Effusion

 G1=gas 1 G2=gas 2 Average Kinetic Energy KEG1 = KEG2 when TG1=TG2 Molecular Speed √u2 = √3RT÷M where M is the molar mass √u2G1 ÷ √u2G2 = √MG2 ÷ √MG1 Rate d/dx G1 ÷ d/dx G2 = √MG2 ÷ √MG1 Time tG2 ÷ tG1 = √MG2 ÷ √MG1