8th grade phsical science question?

Question

Here's the picture I took from my science book.

http://i112.photobucket.com/albums/n177/allieandlulu2/help.jpg

It had info you need for the questions below:

Suppose the temperature of a gas in the illustaion (the link i gave you) in Figure 17 was increased to 400 Kelvins (127 Celsus) Predict the new volume of the gas.

Sorry teh picture is a little burry. Plaese tell me how you get teh answer, because I want to learn how to get it.

Answer 1

You need to workout the relationship between the tepperature and volume. If the pressure is kept constant, it would be,

P / T = constant.

You can calculate P/T for for several figures, and you would find out that it is approximately a constant of 0.18 (Use kelvin temperatuen ot celcius tem. OK)

So if nwe volume is P, tempurature is 400K

P/ 400 = 0.18
P = 0.18 x 400 = 72 ml.

Remeber, the whole idea of this data set is to make you work in all possible ways to find out the relationship between P and T and then, to use it in calculations.

Answer 2

PV = RT is the relationship for an ideal gas. R is a consant. So we can also write

P1V1 = RT1 and P2V2=RT2

If Pressure is kept constant we can rewrite the above as:

PV1 = RT1 and PV2 = RT2
and PV1/T1 = PV2/T2
or V1/T1 = V2/T2
You had for 273K, V = 50 ml

So, we can write 50/273 = V2/400
or V2 = 400 X 50 /273 = 73.3 ml approx.

If we use the volume at 100C, we have

69/373 = V2/400 and V2 = 69 X 400 /373 = 74 ml