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## Homework Statement

(a) How many atoms of helium gas fill a balloon of diameter 29.4 cm at 23.5°C and 1.00 atm?

(b) What is the average kinetic energy of the helium atoms?

(c) What is the root-mean-square speed of the helium atoms?

## Homework Equations

P=2/3[N/V][1/2mv^2]

v=srt(3RT/M)

R=8.31

T=23.5 degrees celcius = 296.5K

M(He)=4.0026g/mol

E(int)=3/2nRT

Avogadros #: 6.0221415 × 10^23

## The Attempt at a Solution

(a)I dont know how to find the # of molecules. I know I need Avogadros #.

(b)To solve this, dont I need the first one solved?

(c) v=sqrt((3(8.31)(296.5K))/4.0026 g/mol) = 42.97m/s = 0.0429km/s (which is wrong coz I did this part first)