# Homework Help: Ideal gas mcq

1. Jun 8, 2012

### kalupahana

1. The problem statement, all variables and given/known data
A balloon with a constant volume is in 1000C. The fraction of gas flow out of balloon when temperature increased by 20C is nearly equal to
(consider pressure and the gas in balloon is ideal)

a. 2/373
b. 2/375
c. 2/100
d. 373/375
e. 100/102

2. Relevant equations
PV=nRT
P-pressure
V-volume
n-number of mols
R-universal gas constant
T-temperature

3. The attempt at a solution
In these conditions P,n & R is constant
∴ V α T
V1/V2=T1/T2
V1/V2=375/373

the amount flow out = 375/373-1 = 2/373

but the answer given as as 2/375
the book i get this considered the mass is increasing when temperature increases

in book that was like

PV=(m/M)RT
P,V,M and constant (m-mass of gas, M-molar mass)

m α 1/T
m1T1=m2T2
m1/m2=373/375

the mass flow out = 1-373/375=2/375

which is right

2. Jun 9, 2012

### ehild

The volume of the balloon is constant, but n, the amount of gas in it is different. The pressure is the same at both temperature. You have the equations

PV=n1 R T1
and
PV=n2 R T2.

ehild