Boyle’s+Law

Boyle’s Law:

P1 V1 = P2 V2 Boyle’s Law states that for a fixed amount of gas kept at a fixed temperature, P and V are inversely proportional; this means that while one increases the other decreases. As pressure decreases, volume increases and as pressure increases, volume decreases. Problem: The cylinder of a car’s engine has a volume of 0.6250 L when the piston is at the bottom of the cylinder. When the piston is at the top of the cylinder, the volume is 0.0600 L. If the cylinder is filled with air at an atmospheric pressure of 765.1 mm Hg when the piston is at the bottom, what is the pressure when the piston is at the top of the cylinder? Okay, the first step in solving any gas law problem is to first identify which of the equations you should be using. Because this equation only deals with volume and pressure, it is clear that you will be using Boyle’s Law, the only equation that relates only volume and pressure. P1 V1 = P2 V2 P1 = initial pressure V1 = initial volume P2 = final pressure V2 = final volume Next, determine your givens and what you are solving for. The equation tells you both the volume and pressure of the cylinder when the piston is at the bottom: 0.6250 L at an atmospheric pressure of 765.1 mm Hg; these are your givens for P1 and V1. It also tells you the volume at the top of the cylinder, 0.0600 L. You are trying to solve for the pressure when the piston is at the top of the cylinder; this will be P2. Substitute your known values into the equation. P1 and V1 will be the values given for when the piston is at the cylinder’s bottom, P2 and V2 the top… P1 V1 = P2 V2 (765.1 mm Hg) (0.6250 L) = P2 (0.0600 L)  Now just solve for your unknown, P2. To do this, just isolate the unknown variable. Because P2 is multiplied by 0.600 L, to isolate it you just divide both sides by 0.0600 L… (765.1 mm Hg) (0.6250 L) / (0.0600 L) = P2  Then just solve the equation. P2 = 7969 mm Hg The final answer for P2 is 7969 mm Hg, the problem is solved! :]



Back to main page.