2 Summary of Gas LawsThe gas laws can be summarized as follows:
3 Combined Gas LawThe combined gas law uses Boyle’s Law, Charles’s Law, and Gay-Lussac’s Law (n is constant).P1 V1 = P2V2T T2
4 Combined Gas Law Calculation A sample of helium gas has a volume of L, a pressure of atm and a temperature of 29 °C. At what temperature (°C) will the helium have a volume of 90.0 mL and a pressure of 3.20 atm (n constant)?Step 1 Set up data table:Conditions 1 Conditions 2P1 = atm P2 = 3.20 atmV1 = L (180 mL) V2 = 90.0 mLT1 = 29 °C = 302 K T2 = ?
5 Combined Gas Law Calculation (continued) STEP 2 Solve for T2 P1 V1 = P2 V2T1 T2T2 = T1 x P2 x V2P V1STEP 3 Substitute values to solve for unknown.T2 = 302 K x atm x mL = K0.800 atm mLT2 = 604 K 273 = 331 °C
6 Learning CheckA gas has a volume of 675 mL at 35 °C and atm pressure. What is the volume (mL) of the gas at -95 °C and a pressure of 802 mmHg (n constant)?
7 Solution STEP 1 Set up data table Conditions 1 Conditions 2 T1 = 308 K T2 = -95 °C = 178 KV1 = 675 mL V2 = ?P1 = 646 mmHg P2 = 802 mmHgSTEP 2 Solve for V2V2 = V1 x P1 x T2P T1STEP 3 Substitute values to solve for unknown.V2 = mL x mmHg x 178 K = mL802 mmHg x 308 K