combined-gas-law.ppt
- 2. KEEP IN MIND Gas properties can be modeled using math. Model depends on— V = volume of the gas (L) T = temperature (K) ALL temperatures in the entire chapter MUST be in Kelvin n = amount (moles) P = pressure (atmospheres)(atm)
- 3. Combining the Three Gas Laws Jacques Charles Robert Boyle P1V1 = P2V2 V1 T1 = V2 T2 These are all subsets of a more encompassing law: the combined gas law P1 T1 = P2 T2 P1V1 P2V2 T1 T2 = Joseph Louis Gay-Lussac
- 5. Combined Gas Law Equations P1 = P2 T1V2 T2V1 V1 = P2T1V2 T2P1 T2 = P2T1V2 P1V1 T1 = P1T2V1 P2V2 P2 = P1T2V1 T1V2 V2 = P1T2V1 P2T1
- 6. Calculations Using Combined Gas Law A gas has a volume of 675 mL at 35 ° C and 646 mmHg pressure. What is the volume (mL) of the gas at −95 °C and a pressure of 802 mmHg (n is constant)? STEP 1 Organize the data into a table of initial and final conditions. • Analyze the problem and identify the given. • P1 = 646 mmHg • P2 = 802 mmHg • V1 = 675 mL • V2 = ? • T1 = 35 C + 273 = 308 K • T2 = −95 C + 273 • = 178 K
- 7. SOLUTION: STEP 2 Rearrange to solve for unknown quantity V2. STEP 3 Substitute the values into the gas law equation and calculate.
- 8. Learning Check •A sample of helium gas has a volume of 0.180 L, a pressure of 0.800 atm and a temperature of 29°C. What is the new temperature(°C) of the gas at a volume of 90.0 mL and a pressure of 3.20 atm?
- 9. Set up Data Table P1 = 0.800 atm V1 = 180 mL T1 = 302 K P2 = 3.20 atm V2= 90 mL T2 = ?
- 10. Calculation P1 V1 P2 V2 = P1 V1 T2 = P2 V2 T1 T1 T2 T2 = P2 V2 T1 P1 V1 T2 = 3.20 atm x 90.0 mL x 302 K = 604 K 0.800 atm x 180.0 mL T2 = 604 K - 273 = 331 °C
- 11. And now, we pause for this commercial message from STP • OK, so it’s really not THIS kind of STP… • STP in chemistry stands for Standard Temperature and Pressure • Standard Pressure 1 atm (or an equivalent) Torr- 760 t0rr Millimeters of Mercury-760 mmHg Temperature- Kelvin=273K
- 12. Try This One •A sample of neon gas used in a neon sign has a volume of 15 L at STP. What is the volume (L) of the neon gas at 2.0 atm and –25°C?
- 13. Answer the following problems 10 points each • 1. Find the volume of a gas at STP when 2.00 liters is collected at 745.0 mm Hg and 25.0 degrees Celsius. • 2. A 2.5 L of nitrogen gas exerts a pressure of 760 mmHg at 473 K. What temperature is needed to reduce the volume to 1.75 L at 1140 torr?
- 14. • 3. The pressure of the gas increases from 500 torr to 800 torr as its temperature decreases 75 degrees Celsius to 50 degrees Celcius. If the final volume of the gas is 125 ml then calculate the original volume of the gas.
- 15. Assignment: • 1. Write examples of life applications of Combined gas Law. • 2. Read something about Chemical Reactions.