Posted by **sweety** on Friday, April 3, 2009 at 1:17am.

Oxygen gas having a volume of 784 cm3 at 23.3°C and 1.03 x 105 Pa expands until its volume is 1170 cm3 and its pressure is 1.07 x 105 Pa. Find (a) the number of moles of oxygen present and (b) the final temperature of the sample. (Unit kelvin, K, for part (b).)

- physics -
**drwls**, Friday, April 3, 2009 at 1:47am
Use the perfect gas law to get the number of moles, n. You can use initial condition values of p, V and T . The inital T is 296.5 K, V is 0.784 l and p = 1.017 atm. R = 0.08205 l-atm/mole

n = PV/RT = 0.0328 moles

The temperature after expansion depends upon the type of expansion. Usually an isentropic expansion is assumed, with the gas doing work while it pushes against an external boundary or gas. If it expands into a larger volume that had been previously empty, the gas temperature will not change.

For an isentropic expansion of a diatomic gas,

T^(5/2) * V = constant

The 5/2 exponent equals 1/[gamma - 1].

gamma = 1.4 for diatomics

(T'/296.5)^2.5 = 784/1170 = 0.670

T'/296.5 = 0.852

t' = 252.6 K = -20.6 C

- physics -
**sweety**, Friday, April 3, 2009 at 10:04am
thank u so much for the help

- physics -
**drwls**, Friday, April 3, 2009 at 10:34am
T' is supposed to be the final temperature

## Answer This Question

## Related Questions

- Intro to Physics - (a) An ideal gas occupies a volume of 3.0 cm3 at 20°C and ...
- CHEMISTRY!! D: - 1. A sample of gas under a pressure of 622 kPa has a volume of...
- Chemistry;HELP - 1. A sample of gas under a pressure of 622 kPa has a volume of...
- physics - pls.. help me with this i really need it.. pls. A gas in a cylinder ...
- physics/chemistry - (a) An ideal gas occupies a volume of 1.0 cm3 at 20°C and ...
- Physics - (a) An ideal gas occupies a volume of 1.6-cm3 at 20°C and atmospheric ...
- chemistry - a sample of oxygen gas has a volume of 2730 cm3 at 21.0 C. At what ...
- chemistry - At a pressure of 405 kPa, the volume of a gas is 6.00 cm3. Assuming ...
- Chemistry;HELP - 1. What volume will a sample of hydrogen occupy at 128.0 oC if...
- Chemistry - 1. A cylinder of Xenon has a volume of 750. ml. At 25.0°C the ...

More Related Questions