How to Calculate the Effusion Rate of Oxygen from a Balloon?

[Zvaigzdute]

Homework Statement

Suppose we make a circular hole 2 millimeter in diameter in a balloon. Calculate the initial rate at which oxygen escapes through the hole (at 0° C), in number of oxygen atoms leaving the balloon per second.

Homework Equations

1/4 n*A*v

The Attempt at a Solution

1/4 n*A*v

n = N/V at # of molecules/m^3 (density)
n = 6.022e23/.0224 = 2.68839286E25
This is at STP so 22.4 L volume at one mol of gas

A = area
Pi*.0002^2*1/4 = 3.14159265 × 10-8

V = velocity
= sqrt(3*k*T/m)
=
k = Boltzmann constant 1.4e-23
T = 273K at STP
m = 2.65780731e-26 kg for one molecule of hydrogen

Atoms/second = 656.816755


What am I doing wrong?

 

[nasu]

Area is of the order of 10^(-6) and not 10^(-8).
Radius, R=1mm=10^(-3)m
A=pi*10^(-6)