# Need help with Boyles Law?

Im taking chemistry this year and we are learning Boyles law. It is P1 times V1= P2 times V2. Im having trouble with his law. I have three questions I need help with. My teacher gave me the answers so don't just supply answers or I won't give you the points. I need to show work. so please show me all the work you have to do and tell me what is P1, P2, V1, V2 in the problems. Answers are all in significant figures.

1. Part of the reason that conventional explosives cause so much damage is that their detonation produces a strong shock wave that can knock things down. While using explosives to knock down a building, the shock wave can be strong that 12 liters of gas will reach a pressure of 3.8 time 10^4 mm Hg. When the shock wave passes and the gas returns to a pressure of 760 mm Hg, what will the volume of that gas be?

2. Submarines need to be extremely strong to withstand the extremely high pressure of water pushing down on them. An experimental research submarine with a volume of 15,000 liters has an internal pressure of 1.2 atm. If the pressure of the ocean breaks the submarine forming a bubble with a pressure of 250 atm pushing on it, how big will that bubble be? the answer is 72 L.

3. Divers get "the bends" if they come up too fast because gas in their blood expands, forming bubbles in their blood. If a diver has 0.05L of gas in his blood under a pressure of 250 atm, then rises instantaneously to a depth where his blood has a pressure of 50.0 atm, what will the volume of gas in his blood be? Do you think this will harm the diver?

Relevance

Boyle’s law tells us that the volume of a gas is inversely proportional to the pressure on the outside of the container holding the gas. Say you inflate a balloon and took it 500 ft under water. The water pressure on the outside of the balloon would cause the balloon to get smaller. Greater pressure, less volume and inversely, less pressure, greater volume.

If you took the same balloon 50 miles up into the atmosphere, where the pressure is less, the balloon would get bigger.

The actual reason for the volume of the balloon increasing is that the number of gas molecules hitting the outside surface of the balloon is less up high in the atmosphere.

Boyle’s law equation

P1 * V1 = P2 * V2

1. Part of the reason that conventional explosives cause so much damage is that their detonation produces a strong shock wave that can knock things down. While using explosives to knock down a building, the shock wave can be strong that 12 liters of gas will reach a pressure of 3.8 time 10^4 mm Hg. When the shock wave passes and the gas returns to a pressure of 760 mm Hg, what will the volume of that gas be?

You say you have a problem determining what numbers are what variables.

P1 and V1 are the pressure and volume before a change occurs.

P2 and V2 are the pressure and volume after a change occurs.

Another way to determine what numbers are what variables is to look at the units.

Units of volume are Liters, ml, cc cubic meters

Units of pressure are atmospheres, mm Hg, Pascal

While using explosives to knock down a building, the shock wave can be strong that 12 liters of gas will reach a pressure of 3.8 time 10^4 mm Hg.

Which number is P1?

Which number is V1?

Which number is P2?

Which number is V2?

Do not look at the answers below, yet!!

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P1 = 3.8 * 10^4 mm Hg

V1 = 12 L

P2 = 760 mmHg

V2 = ?

P1 * V1 = P2 * V

3.8 * 10^4 * 12 = 760 * V2

Solve for V2

V2 = 600 L

2. Submarines need to be extremely strong to withstand the extremely high pressure of water pushing down on them. An experimental research submarine with a volume of 15,000 liters has an internal pressure of 1.2 atm. If the pressure of the ocean breaks the submarine forming a bubble with a pressure of 250 atm pushing on it, how big will that bubble be? the answer is 72 L.

P1 = 1.2 atm

V1 = 15,000 liters

P2 = 250 atm

V2 = ?

P1 * V1 = P2 * V

1.2 * 15,000 = 250 * V2

Solve for V2

V2 = 72 L

3. Divers get "the bends" if they come up too fast because gas in their blood expands, forming bubbles in their blood. If a diver has 0.05L of gas in his blood under a pressure of 250 atm, then rises instantaneously to a depth where his blood has a pressure of 50.0 atm, what will the volume of gas in his blood be? Do you think this will harm the diver?

P1 = 250 atm

V1 = 0.05 L

P2 = 50 atm

V2 = ?

This is a great problem to solve by logic. The new pressure is 1/5 5 times the original pressure, so the new volume will be 5 times the original volume

5 * 0.05 = 0.25 L

P1 * V1 = P2 * V

250 * 0.05 = 50 * V2

Solve for V2

V2 = 0.25 L

Source(s): 23 years of teaching chemistry and physics
• Boyle's Law actually has a constant pressure. The loss of air in this question seems to indicate a pressure change, so Charles' Law would be the better explanation.

• 12 x 3.8 x 10^4 = V x 760

V = 600 L

15000 x 1.2 = V x 250

V = 72 L

0.05 x 250 = V x 50.0

V = 0.25 L