1ST Q Science 10 (LH2) - Gas Laws - Abocado PDF

Gas Laws Violeta H. Abocado  LESSON SCOPE ◆ Lecture Objectives ◆ Describe the general properties of gases ◆ Explain the diff erent laws of gases using the Kinetic Molecular Theory (KMT) ◆ Use Gas’ Laws to determine the properties of a given sample of...

Gas Laws Violeta H. Abocado  LESSON SCOPE ◆ Lecture Objectives ◆ Describe the general properties of gases ◆ Explain the diff erent laws of gases using the Kinetic Molecular Theory (KMT) ◆ Use Gas’ Laws to determine the properties of a given sample of gas ◆ Apply Dalton’s Law of Partial Pressures to a mixture of Gases 2  LESSON SCOPE ◆ Part 1: Concept of gases Characteristics of gases Kinetic molecular theory Properties of gases ◆ Conversions Converting between diff erent units in calculations for pressure, amount of substance, and temperature The Standard Temperature and Pressure (STP) 3  LESSON SCOPE ◆ Part 2: Gas laws Avogadro’s L aw Graham’s Law of eff usion V -n relationship Boyle’s L a w Conversion of moles to P-V relationship grams and vice versa Charles’ L a w Ideal G a s L a w V-T relationship Proportionality constant G ay-Lussac’s L aw P-V-T-n relationship P-T relationship D alton’s L a w of PartialPressure Co m b in e d G a s L a w In conjunction with other gas P-V-T relationship laws 4  III. GAS LAWS 5  GAS LAWS ◆ Gas Laws 1. Boyle’s Law P V P V T constant Robert Boyle Describes the inverse relationship between vo l u m e a n d pressure at const ant temperature. 6  GAS LAWS ◆ A visual representation of Boyle’s law illustrates that the larger the volume, the lesser the pressure and vice versa. ◆ Ga s particles with lesser volume become more compact caused by lesser space in the container. Figure IIb. Boyle’s law with a gas compression device 7  GAS LAWS ◆ One of the real life applications of Boyle’s law is pressurized aerosol sprays we use like air fresheners a n d insect repellants. ◆ Spraying these cans causes release of pressure, decompressing the can and allowing for some volume to occupy given the lesser pressure. Figure IIc-d. Real life applications of Boyle’s law 8  GAS LAWS ◆ The body’s processofrespiration is another example of Boyle’s law. ◆ Inhalation occurs due to an increase in the lung vo l u m e (diaphragm contraction and chest wall expansion) which results in a decrease in lung pressure in comparison to the atmosphere; thus, air rushes in the airway. 9 Figure IIc-d. Real life applications of Boyle’s law  GAS LAWS ◆ Gas Laws 2. Charles’ Law T T P constant Jacques CharlesV (French)V States that the Kelvin tempera ture and volume of gas are directly related when there is n o c h a n ge i n p re s s u re. = 10  GAS LAWS ◆ Charles’ law states that temperature and volume vary directly. ◆ This means the lesser the temperature, the lesser the volume, while higher temperatures (more heat) means the volume of the substance expands as well. Figure IIe. Charles’ law visual representation 11  GAS LAWS ◆ A real-life application of Charles’ law is the mechanic of hot air b a llo o n s. ◆ From the name itself, hot air balloons will not rise up if cold air is pumped into the balloon itself. ◆ Hot air (higher temperature) increases the volume of the balloon until it is enough to rise Figure IIf. Hot air balloons clearly demonstrate the real-life application of Charles’ law up. 12  GAS LAWS ◆ Gas Laws 3. Gay-Lussac’s Law T T V constant Joseph Louis Gay-Lussac P P (French) T he pressure of gas is directly proportional to its Kelvin temperature, with constant volume. 13  GAS LAWS ◆. Gay-Lussac’s law states a direct relationship between pressure and temperature ◆ As shown in the fi gure, gas particles under the cold would not move much, but if boiling water were to be added in a container of air, particles would move faster and collide, thus increasing Figure IIh. Gay-Lussac’s law visual pressure. representation 14  GAS LAWS ◆ A real-life application of Gay- Lussac’s law is a car tire on extremely hot wea ther. ◆ T he air inside tires are heated up on hot weather. When the tire’s elasticity can no longer handle the increasing pressure brought by increased air temperature, the tire ‘explodes’ Figure IIi. Car tires as a real life application of Gay-Lussac’s law as shown in the fi gure. 15  GAY- LUSSAC’S LAW PROBLEM APPLICATION: A sample of gas at exerts a pressure of 1.6 atm. Calculate the new pressure [in atm.] if the temperature is changed to 60 at constant volume. Given: T1= + 273 = 294 K T2 = 60 + 273 = 333K P1 = 1.6 atm. Asked: New pressure; P2 Solution: Gay- Lussac’s Law: Answer: P2= 1.81 atm. = 1.6 atm. [ 333K] = P2 [294 K] P2 = = 1.81 atm. 15  GAY- LUSSAC’S LAW PROBLEM APPLICATION: Determine the pressure change when a constant volume of a gas at 1.25 atm. Is heated from 20 to 35. Given: T1= 20 + 273 = 293 K T2 = 35 + 273 = 308K P1= 1.25 atm. Asked: Pressure change Solution: pressure change = P2-P1 = = [1.31 – 1.25]atm. 1.25 atm. [ 308K] = P2 [293 K] = 0.06 atm. P2 = = 1.31 atm. Answer: pressure change = 0.06 15atm.  GAY- LUSSAC’S LAW PROBLEM APPLICATION: A gas in a closed container is pressurized from 15.0 atm. to 16.0 atm. If the original temperature of the gas was 27 , what should be its temperature in ? Given: P1= 15.0 atm. P2 = 16.0 atm. T1 = 27 + 273 = 300K Asked: T2 [ ] Solution: = 15.0 atm.[ T2] = 300K[16.0 atm.] T2 = = 320 K T2 = 320 K – 273 = 47 Answer: T2 = 47 15  GAS LAWS ◆ Gas Laws 4. Combined Gas Law Experiments inside the laboratory do not always follow normal conditions. The customary reference point for gases is 0°C and 1 atm (standard temperature and pressure, aka STP) Enables you to solve for changes in volume, 16 temperature, and pressure.  GAS LAWS ◆ Gas Laws 4. Combined Gas Law 17  GAS LAWS ◆ A real-life application of combined gas law is “the h u m a n body in scuba d ivi ng.” ◆ The pressure in water is greater than pressure in air, and water pressure increases with depth. With each Figure IIj. The body’s physics during scuba additional foot that divers diving is an application of the combined gas descend, water pressure rises. law. 18  Combined gas law A 20 mL bubble is released from a tank at a pressure of 4.0 atm. And a temperature of 10. What will be the volume of the bubble when it reaches the water surface where the pressure is 1.0 atm. And temperature is 19. Given: P1 = 4.0 atm. T1 = 10 + 273 = 283 K V1= 20 mL P2 = 1.0 atm. T2 = 19 + 273 = 292 K V2 =? Solution: =  Combined gas law = = = V2 = = 82.54 mL Answer. V2 = 82.54 mL  Combined gas law PRACTICE EXERCISE: COMBINED GAS LAW A gas is confined in a closed vessel with a volume of 12 Liters. Temperature is at 35 and a pressure of 1.85 atm. Suddenly temperature increases to 55 and pressure dropped to 1.15 atm. Calculate the new volume of the gas in Liters.  GAS LAWS ◆ Gas Laws 5. Avogadro’s Law V n V n T, P constant Amedeo Avogadro The volume of gas is directly related to the n u m b e r of m ol e s ( n) w h e n temperature a nd pressure are constant.  GAS LAWS ◆ Avogadro’s law states a direct relationship b e t we e n m o l e s and volume. ◆ According to the fi gure, the more moles a container has, the more volume of gas. ◆ This is the same as well when moles are decreased. ◆ This is only possible when Figure IIk. A schematic illustration of temperature and pressure do Avogadro’s law not change. 20  GAS LAWS ◆ An real-life example of Avogadro’s law are helium balloons. ◆ Helium balloons are much more lighter than the usual oxygen-fi lled balloons as helium is less dense than oxygen. ◆ This is why helium balloons rise up while regular balloons stay on the ground. Figure IIL. Helium balloons are a real-life application of Avogadro’s law ◆ Diff erent gases have diff erent 21 densities.  GAS LAWS ◆ Gas Laws 6. Dalton’s Law of Partial Pressure John Dalton Total pressure exerted by mixture of gases is equal to the sum of partial pressures of the present gases. ++…+ 22  GAS LAWS ◆ Dalton’s law states that partial pressures of each individual gas makes up for the total pressure. ◆ Each gas exerts their own pressure in each container, as shown in the diagram. ◆ W h e n these gases are combined, the sum of pressures is now the pressure of the container. Figure IIm. Schematic illustration of ◆ As long as the gases are non- Dalton’s law reacting, this law applies. 23  GAS LAWS ◆ Gas Laws 7. Ideal Gas Law Based on experimental measurements of gas properties. Combines: Boyle’s, Charles’, Gay-Lussac’s, and Avogadro’s laws. 24  GAS LAWS ◆ Gas Laws 7. Ideal Gas Law R is a proportionality constant that is always present in all equations with the ideal gas law. “ T h e vo l u m e o f a ga s va r i e s d i re ct ly w i t h t h e n u m b e r of m ol e s a n d absolute temperature and inversely proportional w i th pressure.” 25  GAS LAWS ◆ A real-life application of the Ideal Gas Law is the construction of gas co nt a iners s u ch a s L P G s. ◆ Engineers use this equation to compute for the proper volume a gas tank could hold. ◆ For example, if an engineer is told that the container needed to be built can only hold 600g of Oxygen Figure IIo. Construction of LPGs use strictly kept at 1 atm and 125°F, the ideal gas law ideal gas law is used to know how 26 much volumeiscapacity. the  SUMMARY OF FORMULA GAS LAW FORMULA RELATION CONSTANT NOTES Graham’s Law of K=K none Mass increases, Effusion = Mass Velocity velocity decreases; vice Inversely versa proportional Boyle’s Law = P: P Temperature Standard Inversely (T) pressure is 1 proportional atmosphere Charles’ Law = T V: V Pressure ( P) Temperature Directly must be in Kelvin proportional (K) Gay Lussac’s Law = P :P Volume (V) K= Directly proportional Combined Gas = n/a ( it is based Number of moles Need a periodic Law on the three (n) table to get the Laws, B-C-GL) molar mass Avogadro’s Law = V: V Pressure (P), STP: 1 atm. Directly Temperature (T) T= 0 proportional  “ G a s e s a r e di st i ngui s he d f r o m ot h e r fo r m s of m at t e r, n o t o n ly by their p owe r of indef inite e x p a n s i o n s o a s t o fi ll a n y ve s s el , h ow e v e r l a r ge , a n d b y g r e a t e ff e c t h e a t h a s i n d i l at i n g t h e m , b u t t h e u n i fo r m i t y a n d s i mp l i c i t y o f t h e l aws w h i c h reg u l ate th e s e ch a n g e s. ” — James Clerk Maxwell 28