# The gas pressure in a modern television broadcast tube at 20 degrees is about 10 -9 atm.

The gas pressure in a modern television broadcast tube at 20 degrees is about 10 -9 atm. what is the number of molecules in 1 cm 3?

Pressure, concentration of molecules and temperature are related by the dependence:
P = nkT, where k is the Boltzmann constant:
k = 1.38 x 10-23 J / K.
n = p / kT:
1 atm = 101325 Pa.
Pressure P = 10 ^ -9 atm. = 0.000101325 Pa.
We express the temperature in degrees Kelvin: T = 273.16 + 20 = 293.16 K.
Substitute the values:
n = 0.000101325 Pa / 1.38 x 10-23 J / K * 293.16 K = 2.5 * 10 ^ 16 per cubic meter.

There will be a million times less molecules in one cubic centimeter: n1 = 2.5 * 10 ^ -10 per cm cube.

Answer: 2.5 * 10 ^ -10 per cm cube.

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