Presentation on theme: "Kinetic Molecular Theory"— Presentation transcript:
1 Kinetic Molecular Theory The Kinetic Molecular Theory explains the forces between molecules and the energy that they possess. This theory has 3 basic assumptions.
2 1. Matter is composed of small particles (molecules) 1. Matter is composed of small particles (molecules). Volume is the measure of space in between the molecules and not the space the molecules contain themselves.
3 2. The molecules are in constant motion. Solid - Molecules are held close to each other by their attractions of charge. They will bend and/or vibrate, but will stay in close proximity.
4 Liquid - Molecules will flow or glide over one another, but stay toward the bottom of the container. Motion is a bit more random than that of a solid.
5 Gas - Molecules are in continual straight line motion Gas - Molecules are in continual straight line motion. The kinetic energy of the molecule is greater than the attractive force between them, thus they are much farther apart and move freely of each other.
6 3. When the molecules collide with each other, or with the walls of a container, there is no loss of energy.
7 Properties of Gases Gases can be compressed into smaller volumes ↑ P causes ↓ Vso: ↑ P causes ↑density
8 Properties of GasesGases exert pressure on surroundings. So to confine a gas, pressure must be exerted on it. (Newton’s third law: for every action, there is an equal and opposite reaction)
9 Properties of GasesGases expand without limits, therefore a gas will completely fill the container it occupies
10 Gas PropertiesCollisions between gas particles and between particles and the container walls are elastic collisions
11 Properties of GasesGas particles are in constant, rapid, random motion. Have kinetic energy
12 Gas PropertiesFluidity Gas particles glide easily past one another since the attractive forces are minimal.
13 Properties of GasesGases diffuse into one another. Gases mix completely, ie gases are miscible.The amount of gas can be known if the pressure, temperature and volume are known.
14 TEMPERATURE AND KINETIC ENERGY Different substances have the same average KE when they are at the same temperature.The velocity of the particles depends on their atomic or molecular mass (formula weight). The greater their mass, the slower their velocity.
15 Pressure Pressure – force / unit area Units: Newtons / m2 (Pascals) Atmospheres (atm)mm HgTorr1 atm = 14.7 psi = 1.01 x 105 Pa =760 mm Hg = 760 Torr =101.3kPa
26 A balloon initially occupies 12. 4 L at 1. 00 atm A balloon initially occupies 12.4 L at 1.00 atm. What will be the volume at atm?P1V1 = P2V2P1=1.00 atmV1=12.4 LP2=0.800 atmV2=?1.00 atm * 12.4L = V2*0.800 atmP1V1 = V2P2V2=15.5L
27 A 5. 00 L container is filled with gas at 1. 00 atm A 5.00 L container is filled with gas at 1.00 atm. A piston then compresses the gas to L. What is the new pressure?P2 =?P1 =1.00 atmV2 =0.250LV1 =5.00 L1.00 atm* 5.00 L = 0.250L *XP1V1 = P2V2P1V1 = V2P2X = 20.0atm
28 Example #3: 2. 50 L of a gas was at an unknown pressure Example #3: 2.50 L of a gas was at an unknown pressure. However, at standard pressure, its volume was measured to be 8.00 L. What was the unknown pressure?End E 4/7
29 As the temperature increases, the volume increases. Charles LawAs the temperature increases, the volume increases.(in K not oC)↑ T causes ↑ VV/T = constantV1/T1 = V2/T2
32 Charles’s LawIf the amount of a gas and its pressure remain constant, thenAs the temperature of a gas increases, the volume of the gas increases.↑T =↑VAs the temperature of a gas decreases, the volume of the gas decreases↓T =↓V
33 V1/T1 = V2/T2 (T2*V1)/T1 = V2 691 mL = V2 A 450 mL piston assembly containing gas initiallyat 293 K is suddenly heated to 450 K.What will be the new volume of the piston assembly?V1=450 mLT1=293 K(T2*V1)/T1 = V2V2=?T2=450K(450K *450 mL)/293 K=V2691 mL = V2
34 Example #2: 4. 40 L of a gas is collected at 50. 0°C Example #2: 4.40 L of a gas is collected at 50.0°C. What will be its volume upon cooling to 25.0°C?
35 Example #3: 5.00 L of a gas is collected at 100 K and then allowed to expand to 20.0 L. What must the new temperature be in order to maintain the same pressure?
36 KELVINSEVERY TEMPERATURE USED IN A CALCULATION MUST BE IN KELVINS, NOT DEGREES CELSIUS.
37 Increased Temperature = Increased Pressure Gay –Lussac’s LawThe pressure of a fixed mass of gas at a constant volume varies directly with the Kelvin TemperatureOrIncreased Temperature = Increased Pressure
38 Gay –Lussac’s LawIf the temperature of a container is increased, the pressure increases.↑T =↑PIf the temperature of a container is decreased, the pressure decreases.↓T =↓P
39 Don’t forget temperature is in Kelvin Gay –Lussac’s LawP P2T T2Don’t forget temperature is in Kelvin=
40 If the pressure of a chamber was 100 atm at 600 K, what will be the temperature of the chamber if the pressure was raised to 600 atm?P1=100 atmP2=600 atmT1=600KT2=? K600 atm100 atmP1 = P2T T2=? K600K
41 100 atm600 atm=600K? K? K *100 atm=600 atm *600K
42 ? K = 600 atm * 600K 100 atm ? K = ? K = 3600K 100 atm 600 atm = 600K
43 Example #2: 5. 00 L of a gas is collected at 22. 0°C and 745. 0 mmHg Example #2: 5.00 L of a gas is collected at 22.0°C and mmHg. When the temperature is changed to standard, what is the new pressure?
44 Avogadro's LawGives the relationship between volume and amount when pressure and temperature are held constant.V1 / n1 = V2 /n2 or V1 = V2n1 n2
45 Avogadro's LawIf the amount of gas in a container is increased, the volume increases.↑n =↑VIf the amount of gas in a container is decreased, the volume decreases.↓n =↓v
46 5. 00 L of a gas is known to contain 0. 965 mol 5.00 L of a gas is known to contain mol. If the amount of gas is increased to 1.80 mol, what new volume will result (at an unchanged temperature and pressure)?
48 Combined Gas Law Write Boyle's Law: P1V1 = P2V2 Multiply by Charles Law:P1V12 / T1 = P2V22 / T2Multiply by Gay-Lussac's Law:P12V12 / T12 = P22V22 / T22Take the square root to get the combined gas law:P1V1 / T1 = P2V2 / T2orP1V1T2 = P2V2T1
49 2. 00 L of a gas is collected at 25. 0°C and 745. 0 mmHg 2.00 L of a gas is collected at 25.0°C and mmHg. What is the volume at STP?P1 = P2 =V1= V2=T1= T2=760 mm Hg745.0 mm HgX2.00 L( )(0+273)P1V1 / T1 = P2V2 / T2745.0mm Hg 2.00L / 298 K = 760 mm Hg *X / 273 KV2 = 1.79 L
50 Ideal Gas Law To derive the Ideal Gas Law, we combine all the gas laws Each of the laws has a constant, k. Each k is different.The product of all the constants (k) is written as R. R depends on the units used.R
51 R =Universal Gas Constant (Write this down) Ideal Gas LawPV= nRTP = PressureV = Volume (must be in Liters)n = number of molesT = Temperature(must be in Kelvin)R =Universal Gas Constant (Write this down)R = (L*atm)/(mol*K)orR = (L*kPa)/(mol*K)R = (L*mm Hg)/(mol*K)
52 How many moles of gases are contained in a can with a volume of 555 mL and a pressure of kPa at 20oC? (R = L*kPa)/(mol*K)N = mole
53 Calculate the pressure exerted by 43 moles of nitrogen in a 65 L cylinder at 5oC? (Since there are no pressure units given you can use any R value you want)P= 15 atmP= 1529 kPaP= mmHg
54 If I have 4 moles of a gas at a pressure of 5 If I have 4 moles of a gas at a pressure of 5.6 atm and a volume of 12 liters, what is the temperature?PV=nRT4 moleP=5.6 atmn =R=(L*atm)/(mol*K)V=12 LT=x5.6 atm *12 L = 4 mol * L* atm *Xmol K67.2 atm L = x L atm/K67.2atm L / L atm /K = x204.6 K
55 A steel tank having a volume of 5. 82 L contains 8 A steel tank having a volume of 5.82 L contains 8.78 g of O2 under a pressure of 1.35 atm. What is the temperature -- in degrees Celsius -- of the O2?PV=nRTR = (L*atm)/mol*K)1.35 atm *5.82L = (8.78g/32g/mol)(0.0821L atm/mol K) T7.874 atm L = T0.0225atm L/KT= K = = 76.5oC
56 A sample of an unknown weighing 2. 1025 grams is found to occupy 2 A sample of an unknown weighing grams is found to occupy L at 22.0°C and .9737atm How many moles of the gas are present?(0.97 atm) (2.85 L) = (n) ( L atm / mol K) (295.0 K)2.775 atm L = n *24.20 L atm/mol2.775 atm L = nL atmmolemole = nMole buck Question What is the molar mass of the unknown gas?