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GAS BEHAVIOUR & GAS LAWS

This document discusses several gas laws including Boyle's law, Charles' law, Gay-Lussac's law, and Avogadro's law. Boyle's law states that at constant temperature, the volume of a gas is inversely proportional to its pressure. Charles' law specifies that at constant pressure, the volume of a gas is directly proportional to its temperature. Gay-Lussac's law describes how pressure and temperature are directly proportional at constant volume. Finally, Avogadro's law concerns the relationship between volume and number of moles of gas at constant temperature and pressure.

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GAS BEHAVIOUR UNDER CHANGING CONDITIONS DR. MAHESWARI JAIKUMAR maheswarijaikumar2103@gmail.com
GAS BEHAVIOUR • All gases generally show similar behaviour when the conditions are normal. • When there is a change in physical conditions like pressure, temperature or volume these show a deviation.
GAS LAWS • Gas laws are laws that analyze the behaviour of gases under changing conditions (Temperature, pressure and volume) • The variables of state like the Pressure, Volume and Temperature of a gas depict its true nature. hence gas laws are relations between these variables.
THREE PRIMARY LAWS OF GAS BEHAVIOUR • Boyle's Law • Charles' Law • Avogadro's Law • (All laws combine into the General Gas Equation and Ideal Gas Law).
TH GAS LAWS & PRESSURE, VOLUME AND TEMPERATURE RELATIONSHIP IS AS FOLLOWS: • Boyle's Law: The Pressure-Volume Law • Charles' Law: The Temperature-Volume Law • Gay-Lussac's Law: The Pressure Temperature Law. • The Combined Gas Law.
BOYLE’S LAW • Boyle's law, also referred to as the Boyle–Mariotte law, or Mariotte's law, is an experimental gas law that describes how the pressure of a gas tends to increase as the volume of the container decreases.
• This law states that at a constant temperature, the volume (V) of a given mass of gas is inversely proportional to its pressure (p). • At constant temperature, Boyle’s law can be stated as V ∝ 1/P or VP = constant ….(1)
• The constant is a proportionality constant. • Its values depend on the mass, temperature and nature of the gas. • If P1 and V1 are the initial values of pressure and volume of any gas and P2 and V2 are another set of values, then we can say that • P₁V₁ = constant …(2) and P2V2 = constant …(3)
• Since the mass, temperature and nature of a gas are same throughout, we say equation (2) and (3) represent the same quantity. • Thus we have: P₁V₁ = P2V2
BOYLE’S LAW
INTERPRETATION OF VALUES • P1= first pressure • P2= second pressure • V1= first volume • V2= second volume
BOYLE’S LAW -GRAPH
CHARLES’S LAW • Charles's law is an experimental gas law that describes how gases tend to expand when heated. • A modern statement of Charles's law is: When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be in direct proportion.
• Charle’s law states that at constant pressure, the volume (V) of a given mass of gas is directly proportional to its absolute temperature (T).
• Charles' Law is a special case of the ideal gas law. It states that the volume of a fixed mass of a gas is directly proportional to the temperature. • This law applies to ideal gases held at a constant pressure, where only the volume and temperature are allowed to change.
EXPRESSION OF CHARLES’S LAW • Charles' Law is expressed as: Vi/Ti = Vf/Tf where Vi = initial volume Ti = initial absolute temperature Vf = final volume Tf = final absolute temperature It is extremely important to remember the temperatures are absolute temperatures measured in Kelvin, NOT °C or °F.
• If V is the volume and T is the temperature of a gas at some constant pressure, then V ∝ T or V/T = constant. • Following the same method as above, we can write: V₁/T₁ = V₂/T₂
CHARLE’S LAW
INTERPRETATION OF VALUES • V1= first volume • V2= second volume • T1= first temperature • T2= second temperature
CHARLE’S LAW GRAPH
GAY-LUSSAC'S LAW • Gay-Lussac's Law. ... The French chemist Joseph Gay-Lussac (1778 - 1850) discovered the relationship between the pressure of a gas and its absolute temperature.
• Gay-Lussac's Law states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant.
GAY LUSSACS’ OR REGNAULT’S LAW This law states that at constant volume (V), the pressure (P) of a given mass of a gas is directly proportional to its absolute temperature (T). • We can write: P ∝ T or P/T = constant. Also, we can write: P₁/T₁ = P₂/T₂
• Gay-Lussac's law states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant. • Mathematically, it can be written as: {displaystyle {frac {P}{T}}=k}.
GAY LUSSAC’S GRAPH
AVOGADRO’S LAW • Avogadro’s Law states that equal volumes of different gases, under similar conditions of temperature and pressure, contain equal number molecules.
• This means that if you have two or more different gases, as long as they have similar conditions of temperature and pressure, equal concentrations of these gases will occupy equal portions of volume.
STANDARD GAS EQUATION Gases which obey all gas laws under all conditions of pressure and temperature are called perfect gases or the ideal gases. • Inert gases kept under high temperature and very low pressure behave like ideal gases.
• Equation of state for a perfect gas can be written as PV=nRT ............where, • P = pressure • V = volume • T = absolute temperature • R = universal gas constant = 8.31 J mol- 1 K-1, n = number of moles of a gas
SUMMARY • Avogadro's law – Relationship between volume and number of moles of a gas at constant temperature and pressure. • Boyle's law – Relationship between pressure and volume in a gas at constant temperature • Charles's law – Relationship between volume and temperature of a gas at constant pressure • Combined gas law – Combination of Charles', Boyle's and Gay-Lussac's gas laws
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