Chemistry Review of Gas Laws

Chemistry Review of Gas Laws

Chemistry Review of Gas Laws 150 150 Deborah

Overview:

Substances that exist in gaseous form follow the properties of that state of matter.  Although the random motion of individual atoms and molecules is unpredictable, other properties are not.  Some of these properties of this state of matter are known as the gas laws.

What Is Boyle’s Law?

Boyle’s law relates the pressure of a gas to its volume, when the temperature is kept constant.  The equation is PV = k, where P is pressure, V is volume, and k is a constant.  It can also be expressed as V = k/P, by dividing both sides of the equation by P.  This equation shows that as the volume of a gas decreases, the pressure increases, and as the volume of a gas increases, the pressure decreases in an inverse relationship.  Imagine a cylinder filled with gas at a constant temperature.  Suppose the pressure of the cylinder is increased from 1 to 2.  The volume will decrease to 1/2 of the original volume, so that if the original volume of gas was 500 milliliters, its new volume would be 250 milliliters.

What Is Charles’ Law?

Charles’ law relates to the effect of temperature on the volume of a gas when the pressure is kept constant.  During experiments heating and cooling various types of gases, the volume expanded or contracted by the same amount.  The equation is V/T = k where V is volume, T is temperature in degrees Kelvin, and k is a constant that depends on a fixed mass of the gas.  Imagine a cylinder filled with gas at a constant pressure.  Increasing the temperature causes the molecules to move faster and the volume to expand.  If the temperature is decreased, the molecules inside will move more slowly and the volume to contract.

What Is Gay-Lussac’s Law?

In Boyle’s law, the temperature is kept constant, and in Charles’ law the pressure is kept constant.  In Gay-Lussac’s law, the volume is kept constant, so that the pressure relates to the temperature in the equation P1/T1=P2/T2. This relationship set the stage for the relationships between temperature, pressure, and volume to be combined.

How Are Changes in Temperature, Pressure, and Volume Related?

The combined and ideal gas laws state the relationships between temperature, pressure and volume.  The equation  PV/T = k expresses the relationship between the three variables.  When temperature is held constant, the relationship is that expressed by Boyle’s law.  When pressure is held constant, the relationship is expressed by Charles’ law, and when volume is held constant, the relationship is expressed by Gay-Lussac’s law.

 

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