Help answering this a level question

Lucofthewoods

For the last question the answer is 11.1 but I got 0.0111, can someone tell me how to work this out

Reply 1

1256601

Original post by Lucofthewoods

For the last question the answer is 11.1 but I got 0.0111, can someone tell me how to work this out

mulitply your answer by 1000 to give you volume in dm3, you have volume in m3, pay attention to the units they ask of you! :smile:

Reply 2

Lucofthewoods

Original post by thatawesomekid

mulitply your answer by 1000 to give you volume in dm3, you have volume in m3, pay attention to the units they ask of you! :smile:

sorry this is a silly question but where does it say it's in m3? But thank you!

Reply 3

DisturbedCustard

Original post by Lucofthewoods

For the last question the answer is 11.1 but I got 0.0111, can someone tell me how to work this out

The
ideal gas equation that you used will give an answer in m3. But the question asked for dm3 so you multiply your answer by 1000.
hope this helps

Reply 4

Lucofthewoods

Original post by DisturbedCustard

The
ideal gas equation that you used will give an answer in m3. But the question asked for dm3 so you multiply your answer by 1000.
hope this helps

So unless told different do you assume it's the standard units?

Reply 5

1256601

Original post by Lucofthewoods

sorry this is a silly question but where does it say it's in m3? But thank you!

Question says to find volume in dm^3 on the second line.
The ideal gas equation (pV=nRT) will always give/ require volume to be in m^3 just as pressure must be in Pa, and temp in K. To convert the volume that you got (0.0111 m^3) to dm^3 you multiply by 1000. You've done the right working, just didn't finish it off by converting to the correct units

Reply 6

charco

Study Forum Helper

Original post by Lucofthewoods

So unless told different do you assume it's the standard units?

This has probably caused confusion because the ideal gas equation is used with two different sets of units.

With strict SI units you have volume in m³ and pressure in Nm^-2 (Pa)

With the units often used in chemistry you have volume in dm³ and pressure in kPa.

You need to pay attention to the pressure given as this will give yo the volume units.

You should be thankful as a few years ago you could also have pressure in atm, which gives a different value for R (different units), or even pressure in mmHg (Torr).

At least now things are a little more standardised...