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This guide delves into the fundamental Gas Law represented by the equation PV=nRT, where P is pressure, V is volume, n is the number of moles, T is temperature, and R is the universal gas constant. It includes problem-solving examples, illustrating how to calculate gas pressure using variables such as moles and volume under various conditions, including temperature changes and the Combined Gas Law. Learn how pressure and volume interact inversely and how temperature and volume change directly under constant pressure.
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Gas Laws Chapter 13
The Gas Law PV=nRT P = pressure V= volume n= number of moles T= temperature
R – The Proportionality Constant Value depends on units Or
The Gas Law – Problem If 7.0 moles of an ideal gas has a volume of 12.0 L with a temperature of 300 K, what is the pressure in kPa? PV = nRT P = 1454.95 kPa P = 1500 kPa
Combined Gas Law Let’s say we have some O2 gas AND we change some conditions. Would there be anything similar between the two gases?
Combined Gas Law – Problem You have 3 moles of a solution at 300. K and 15 atm in a 2 L container. If the container is heated to 350. K and the volume decreased to 1 L, what will the new pressure be?
Combined Gas Law – Problemc If we know that R1 = R2 and the mass is constant then Replace with numbers
Combined Gas Law – Problem P2 = 35 atm
Pressure & Volume • At constant Temperature • Pressure and Volume vary inversely. • Why? • More collisions More pressure P1V1 = P2V2
P & V – Variations P2 = V2=
P & V – Example Problem If you start with 0.500 L of a gas at 7.0 atm and you move the gas to a container with 3.5 L available, how much pressure will the gas exert? P1 (V1) = P2 (V2) 7.0 atm (0.500 L) = P2 (3.5 L) 1.0 atm = P2
Temperature & Volume At constant Pressure Volume & Temperature vary directly. • Why? • More collisions More Volume
T & V – Variations T2 = V2 =
T & V – Example Problem If a gas is in a balloon with a volume of 12.0 L and at a temperature of 300 K, what will the volume be if you place the balloon in a freezer at 250 K?
S.T.P. • Standard Temperature and Pressure • These are conditions that are universal • Standard Temperature: 0ºC or 273K • Standard Pressure: 1atm or 101.325kPa
S.T.P. – Example Problem What is the volume of 1 mole of CO2 at STP? PV = nRT (1atm)V = (1 mole)(0.0821 [Latm/Kmole])(273K) V= 22.4 L