# The Combined Gas Law The Combined Gas Law

The Combined Gas Law

The Combined Gas Law • The relationship among pressure, volume, and temperature can be mathematically represented by an equation known as the combined gas law. P 1 V 1 = P 2 V 2 T 1 T 2 where: P 1 is the initial pressure and P 2 is the new pressure. V 1 is the initial volume and V 2 is the new volume. T 1 is the initial temperature and T 2 is the new temperature. Temperature must always be in Kelvin!

The Combined Gas Law Ex. (1) If 22. 4 L of a gas at 0. 0 o. C and 1. 29 atm were cooled to a temperature of -30. 0 o. C as it was expanded to a volume of 85. 9 L, what would be its new pressure in atm? P 1 V 1 = P 2 V 2 T 1 T 2 (1. 29 atm)(22. 4 L) = (X)(85. 9 L) 273. 0 K 243. 0 K X = 0. 299 atm

The Combined Gas Law Ex. (2) If 82. 7 L of xenon gas at 142. 9 k. Pa & 50. 3 o. C were compressed to a volume of 28. 3 L and then was returned to standard pressure, what would be its new Kelvin temperature? P 1 V 1 = P 2 V 2 T 1 T 2 (142. 9 k. Pa)(82. 7 L) = (101. 3 k. Pa)(28. 3 L) 323. 3 K X X = 78. 4 K

The Combined Gas Law Ex. (3) If 3. 75 L of chlorine gas at 20. 0 o. C and 105. 0 k. Pa were returned to STP conditions, what would be the new volume? P 1 V 1 = P 2 V 2 T 1 T 2 (105. 0 k. Pa)(3. 75 L) = (101. 3 k. Pa)(X) 293. 0 K 273. 0 K X = 3. 62 L

The Combined Gas Law Ex. (4) If 25. 0 L of a gas at STP were heated to a temperature of 39. 0 o. C and the volume expanded to 68. 3 L, then what would be the new pressure in atm? P 1 V 1 = P 2 V 2 T 1 T 2 (1. 00 atm)(25. 0 L) = (X)(68. 3 L) 273. 0 K 312. 0 K P 2 = 0. 418 atm

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