Chemistry: Boyle's Law (Gas Laws) with 2 example problems

Pressure and volume of a gas are inversely proportional. As pressure increases, volume decreases, and vice versa, assuming all other factors are constant. This is because compressing a gas means particles collide more frequently with container walls, leading to higher pressure.

Robert Boyle formally stated this inverse relationship as Boyle's Law: for a given amount of gas at a fixed temperature, pressure (P) and volume (V) are inversely proportional (P ∝ 1/V). This can be written mathematically as P = k/V or PV = k, where k is a constant.

Boyle's Law is often used to compare two situations (before and after) and can be expressed as P1V1 = P2V2, where P1 and V1 are the initial pressure and volume, and P2 and V2 are the final pressure and volume.

An example calculates the new tire pressure when a tire's volume changes. Given an initial volume of 11.41 L and pressure of 44 psi, if the volume decreases to 10.6 L, the new pressure (P2) is calculated using P1V1=P2V2, resulting in approximately 47 psi.

Another example involves a syringe with an initial volume of 10.0 ccs and pressure of 1.0 atm. If the pressure is increased to 3.5 atm by pushing the plunger, the final volume (V2) is calculated using Boyle's Law to be 2.9 ccs.

The video briefly introduces other gas laws: Charles's Law (temperature and volume), Gay-Lussac's Law (pressure and temperature), the Combined Gas Law (temperature, pressure, volume), and Avogadro’s Law (volume and amount of gas). All these laws require the amount of gas to be constant, except Avogadro's Law. Combining all four leads to the Ideal Gas Law.

To determine which gas law to use for a problem, identify the known and unknown variables. If a variable is not mentioned or is constant, it may not be needed in the equation.