How many moles of gas are there in a gas filled balloon which has a volume of 67.0 L at a pressure of....?

Question

742 mmHg and a temperature of 25.0 degrees C?

a) 2.24 mol
b) 2.67 mol
c) 2.81 mol
d) 31.9 mol
e) 1.71 x 10(^3) mol

Answer 1

first you have to transform your mesurements. The 25 degrees Celcius has to be converted to Kelvin, and the pressure has to be converted to kPa.
*Since the absolute zero is 0K ans -273C, when transforming the temperature from C to K you get 298K with a simple addition.
*Because the normal pressure is 101.325kPa=760mmHg, a simple multiplication gives 742mmHg=98.8kPa.
Now you can use the gas law, PV=nRT. You want the number of moles, so you have to do n=PV/RT where R=8.31 (it's a constant, it's always 8.31 kPa.L/mol.K)
n=98.8*67/8.31*298=2.67
answer B

Answer 2

pV = nrT, r = 8.314 J/(K mol), T is Kelvins, p in Pascals, v is cubic meters, and n is moles.


Doug