How to Convert a Number Concentration into Volume Mixing Ratio?

• Chemistry
• Geo_Zegarra2018
In summary, the conversation discusses converting a number concentration of 15 x 10^12 molecule/cm3 into volume mixing ratio at different pressure and temperature conditions. It also mentions using the Ideal Gas Law to calculate Loshmidt's number and the density of the atmosphere at STP. The conversation ends with a discussion on understanding the definition and units of volume mixing ratio in order to solve the problem.
Geo_Zegarra2018

Homework Statement

Convert a number concentration of 15 X 10^12 molecule/cm3 into volume mixing ratio at:

a) 1 atm pressure, and 20 C temperature.

b) 500 mbar pressure, and 253 K temperature.

Using the Ideal Gas Law, calculate:

a) Loshmidt’s number (# of molecules/cm3 of air, at standard atmospheric conditions “STP”, 1 atm pressure, and 273 K)

b) Density of atmosphere at “STP”

The Attempt at a Solution

[/B]
I converted 15 x 10^12 molecule/cm^3 to mol/cm^3

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How is the volume mixing ratio defined (I hate the way gases are treated in the atmosphere sciences, they define everything their own way just as if to make things incomprehensible to physicists and chemists )? What information do you need to directly apply this definition?

Bystander
I honestly don’t know. Like if it told me what units to solve for I would probably have a better idea how to proceed this problem

Then you have to google for the definition or find it in your notes. That's your starting point.

1. How do you convert a number concentration of 15 X 10^12 molecule/cm3 into volume mixing ratio?

To convert a number concentration of 15 X 10^12 molecule/cm3 into volume mixing ratio, you will need to know the molar mass of the substance in question. Then, divide the number concentration by Avogadro's number (6.022 X 10^23) and multiply by the molar mass. This will give you the number of moles per cm3. Finally, divide the number of moles by the total number of moles in the mixture to get the volume mixing ratio.

2. What is the formula for converting number concentration to volume mixing ratio?

The formula for converting number concentration to volume mixing ratio is: (number concentration / Avogadro's number) x molar mass / total number of moles in the mixture.

3. Why is it important to convert from number concentration to volume mixing ratio?

Converting from number concentration to volume mixing ratio is important because it allows for a more accurate representation of the concentration of a substance in a mixture. Volume mixing ratio takes into account the molar mass of the substance and the total number of moles in the mixture, providing a more comprehensive measure of concentration.

4. Can you convert number concentration to volume mixing ratio for any type of substance?

Yes, you can convert number concentration to volume mixing ratio for any type of substance as long as you know the molar mass and the total number of moles in the mixture. This method is commonly used in atmospheric science to calculate the concentration of gases in the Earth's atmosphere.

5. Is there a specific unit for volume mixing ratio?

Yes, volume mixing ratio is typically expressed in parts per million (ppm) or parts per billion (ppb). These units represent the number of molecules of a substance per million or billion molecules in the entire mixture.

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