Combined Gas Law: (P_1*V_1)/T_1 = (P_2*V_2)/T_2?

Question

I'm looking for some simple examples of the combined gas law; I need one or two more examples. I was try ing to make an example (for a short paper) of blowing up a ballon, but I can not correlate the variables in the equation for this example.

could I get an example?

Answer 1

e.g. 1..25L of gas has a pressure of 900mmHg at a temperature of 147°C. What is its volume at STP.
(STP Standard Temperature & Pressure. (273 K and 1 atm.)
(1atm = 760mmHg)
°C must be changed to K (°C+273)
Combined Gas Formula: P1V1/T1 = P2V2/T2
P1V1T2 = P2V2T1
P1 (900mmHg initial) x V1 (25L initial) x T2 (273 final) =
P2 (760mmHg final) x V2 (STP) x T1(147°C (420 initial).

900 x 25 x 273 = 760 x V2 x 420
V2 = (900 x 25 x 273) ÷ (760 x 420)
Volume at STP (V2) = 6,142,500 ÷ 319,200 = 19.24 L.

e.g. 2....250L of gas at 3.0atm. is heated from 85°C to 250°C. What is its final pressure, in torr, if the volume remains constant.
(STP Standard Temperature & Pressure. (273 K and 1 atm.)
(1atm = 760mmHg = 760torr)
°C must be changed to K (°C+273)
In this case, at constant volume, we don't need the full Combined Gas Law. Gay Lussac's Law will be sufficient.
(At constant volume, Temperature Increase = Pressure Increase in Direct Proportion.)
P1 x T2 = P2 x T1
3atm x 250°C (523 K) = P2 x 85°C (358 K)
P2 = (3 x 523) ÷ 358
Final pressure (P2) = 1,569 ÷ 358 = 4.4 atm.
= 4.4atm x 760 torr/atm = 3,344 torr.

How do those suit your needs ?

Answer 2

Blow up a balloon with helium or hydrogen. Now you have a fixed amount of gas. Measure the T and V. Assume that P is atmospheric, and that the balloon is infinitely flexible. Let go the balloon. It rises into the upper atmosphere where the pressure is less and the temperature is colder. Select some values of the new T and P and compute V.

Answer 3

PV over T=K

where:

P is the pressure.
V is the volume.
T is the temperature (measured in kelvin).
k is a constant with units of energy divided by temperature.

For comparing the same substance under two different sets of conditions, the law can be written as:


{P1 TIMES V1}div by{T_1}={P2 TIMES V2}{T_2}

Answer 4

Car tire changing air pressure with the change in temperature. Temperature change in tires can occure from weather or from driving. Tire is a fixed volume, T1 and T2 is the change in temperature, and P will be your variable. The balloon example will not work because it is not a closed system. You are adding mass when you blow up a balloon.

Correction: you could use Steve's example for the balloon.

Answer 5

Ever take a helium balloon out into the cold? Ever notice how it deflates and droops but is fine again once you're back in warm air?

There ya go.

P1V1/T1 = P2V2/T2

(1atm * 1 L)/100K = (1atm*V2)/ 50K

Therefore, the volume in the cold air would be the V2 that you would solve for.. It will be less than the first volume and would show why the balloon deflates in cold air.

Answer 6

use PV=nRT