# The Nature of Gases Chapter 6 Gases 6.6 The Combined Gas Law 1 Combined Gas Law The combined gas law uses Boyles Law, Charles Law, and Gay-Lussacs Law (n is constant). P1 V 1 = T1 P2 V 2

T2 2 Learning Check A gas has a volume of 675 mL at 35C and 0.850 atm pressure. What is the volume(mL) of the gas at -95C and a pressure of 802 mm Hg (n constant)? 3 Solution Conditions 1 T1 = 308 K

Data Table Conditions 2 T2 = -95C + 273 = 178K V1 = 675 mL V2 = ??? P1 = 646 mm Hg P2 = 802 mm Hg Solve for V2 V2 = V1 x P1 x T2 P2

T1 V2 = 675 mL x 646 mm Hg x 178K = 314 mL 802 mm Hg x 308K 4 Combined Gas Law Calculation A sample of helium gas has a volume of 0.180 L, a pressure of 0.800 atm and a temperature of 29C. At what temperature (C) will the helium have a volume of 90.0 mL and a pressure of 3.20 atm (n is constant)? 1. Set up Data Table Conditions 1 Conditions 2 P1 = 0.800 atm

P2 = 3.20 atm V1 = 0.180 L (180 mL) V2 = 90.0 mL T1 = 29C + 273 = 302 K T2 = ?? 5 Combined Gas Law Calculation (continued) 2. Solve for T2 P1 V1 = T1

P2 V2 T2 T2 = T1 x P2 x V2 P1 V1 T2 = 302 K x 3.20 atm x 90.0 mL = 604 K 0.800 atm 180.0 mL T2 = 604 K - 273 = 331 C 6