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# I need help with boyle's law calculations.?

i need a really easy tutorial to do this stuff. I took all the notes in my chem class and I still don't understand. HELP.

the Directions say: using boyle's law P1V1=P2V2 calculate the missing variable. Temperature is constant. P1 is original pressure, V1 is original volume P2 is new(changed) pressure, V2 is the new(changed) volume.

here is one of the example questions that they gave us, but i did not understand at all!

If 425 cm(cubed) of oxygen were collected at a pressure of 9.80 kPa what volume will the gas occupy if the pressure changed to 9.40 kPa

help will be greatly appreciated, and the one who explains it to me the best will get to 10 points.

### 3 Answers

- Anonymous1 decade agoFavorite Answer
For this problem, and other Boyle's Law calculations, you will need to rearrange your given equation P1V1=P2V2 to solve for the unknown. In your case, you would like to find V2, which represents the volume after a change in pressure.

So...

Let V1 = initial volume = 425 cm^3

Let P1 = initial pressure = 9.80 kPa

Let P2 = final pressure = 9.40 kPa

V2 = ???

Rearrange the equation P1V1=P2V2 to solve for V2. To do this, divide both sides by P2, resulting in the following equation:

P1V1/P2 = V2

(initial volume times initial pressure divided by final pressure equals the final volume)

Plug in your knowns (P1,V1,P2) and solve for V2.

Your final answer should be 443 cm^3

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- Anonymous1 decade ago
Its asking you exactly what the equation means. You start out with 425cm2 of oxygen at a pressure of 9.80 kPa. And you want to figure out what the new volume will be when the pressure becomes 9.40kPa. So you plug it in like

P1V1=P2V2

9.80kPa(425cm2)=9.40kPaV2.

It's easiest to isolate the variable you're trying to figure for (V2) by dividing both sides by P2.

So next you would write

V2=(9.80kPa[425cm2])/9.40kPa

Just multiply P1 and V1, then divide your answer by P2.

When gas molecules are exposed to different pressures, their volume changes accordingly. Just like if they're put into a larger container and the volume increases, the pressure will decrease. If you have 3 of the variables, you can solve for the fourth just like any other mathematical equation.

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- Dr. Merlin BachLv 41 decade ago
P1V1=P2V2

(9.80 kPa)(425 cm^3)= (9.40 kPa)(x)

4165=9.40x

x=443 cm^3

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