# A Pipe Filled with Helium

1. Apr 13, 2007

### GreenMind

1. The problem statement, all variables and given/known data
A certain organ pipe, open at both ends, produces a fundamental frequency of 275 Hz in air.

If the pipe is filled with helium at the same temperature, what fundamental frequency f will it produce? Take the molar mass of air to be 28.8 g/mol and the molar mass of helium to be 4.00 g/mol.

2. Relevant equations

below

3. The attempt at a solution
v(he)=999 m/s
v(O)=344 m/s
I solved with $$fn = n v / 2 L$$ but I am not getting as accurately of an answer as id like. How can I incorporate the molar mass into these equations?

2. Apr 13, 2007

### Dick

You'll need to find the relationship between the speed of sound in an ideal gas to the density of the gas. The density is proportional to the molar mass.

3. Apr 13, 2007

### denverdoc

post deleted.