# Help is needed for converting units of a simple formula

• han_123
In summary, the conversation revolves around converting a volume mixing ratio or a mol/mol ratio to the units of molecules/cm3. The temperature and air density are given, and the goal is to find the number of molecules in one cm3 of the gas. The ideal gas formula and Avogadro's hypothesis are mentioned, but more details are needed to provide a solution.

#### han_123

please post this type of questions in the homework forums, filling out the template
How would you convert a volume mixing ratio [m3/m3] to the units of [molecules/cm3]? The temperature is given to be 293K and the air density is 1 kg/m3. Please help!

[m3/m3] has no physical dimension but [molecules/cm3] has physical dimension of L^-3. I am afraid some more details of the exercise are required to help you.

And do you know how to convert gas volume to number of moles? Number of moles to number of molecules?

Bystander
Borek said:

And do you know how to convert gas volume to number of moles? Number of moles to number of molecules?
Hi! Well not exactly. I know there is the ideal gas formula PV = nRT and that a mole contains the Avogadro number of molecules.

However, I am confused about how to convert a volume mixing ratio [m3/m3] or [mol/mol] to the units of [molecules/cm3] when only the temperature is given to be 293K and the air density is 1 kg/m3.

The goal is to find whenever a gas is mixed into an airspace at a certain ratio then how many molecules of that gas are to be found in one cm3.

anuttarasammyak said:
[m3/m3] has no physical dimension but [molecules/cm3] has physical dimension of L^-3. I am afraid some more details of the exercise are required to help you.
The volume mixing ratio can also be given in [mol/mol]. How do you convert a mol of gas into the number of molecules when only the air density and temperature are given?

The goal is to find whenever a gas is mixed into an airspace at a certain ratio then how many molecules of that gas are to be found in one cm3.

Hint: density at a given temperature is enough to find the pressure.

## 1. How do I convert units in a simple formula?

To convert units in a simple formula, you need to identify the units you are converting from and to. Then, use conversion factors to multiply or divide the original value to get the converted value.

## 2. What are the common conversion factors used in unit conversion?

Common conversion factors include 1 meter = 100 centimeters, 1 kilogram = 1000 grams, and 1 liter = 1000 milliliters. However, the specific conversion factors depend on the units being converted.

## 3. Can I use an online unit converter for simple formulas?

Yes, there are many online unit converters that can help with simple formula conversions. However, it is important to double-check the results and make sure the units are converted correctly.

## 4. How do I know if I need to convert units in a formula?

If the units in the formula do not match or if you need the final result in a different unit, then you will need to convert units in the formula. It is also important to check if the units in the formula are consistent and make sense for the given situation.

## 5. Are there any tips for converting units in a simple formula?

One helpful tip is to write out all the units in the formula and cancel out the units that are the same on both sides of the equation. This will help you identify the conversion factor needed for the remaining units. It is also important to pay attention to significant figures and round the final result to the appropriate number of digits.

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