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# Express as parts per million watch

1. At sea level there is approx 2.6 x10^25 molecules in M^-3 of atmosphere. One of the gases making up atmosphere has a concentration of 2.47 x 10^22 molecules m-3. What is the concentration of this gas in parts per million?

I have no idea?

Can anyone help?
2. (Original post by Lambert87)
At sea level there is approx 2.6 x10^25 molecules in M^-3 of atmosphere. One of the gases making up atmosphere has a concentration of 2.47 x 10^22 molecules m-3. What is the concentration of this gas in parts per million?

I have no idea?

Can anyone help?
Do you know how to find out the concentration as a fraction (or decimal)?
3. (Original post by Lambert87)
At sea level there is approx 2.6 x10^25 molecules in M^-3 of atmosphere. One of the gases making up atmosphere has a concentration of 2.47 x 10^22 molecules m-3. What is the concentration of this gas in parts per million?

I have no idea?

Can anyone help?
So, this gas has 2.47 x10^22 molecules, out of 2.60 x10^25.

Percentages are "parts per hundred".

Find what (2.47e22)/(2.60e25) is as a fraction, when the denominator is one million.

Spoiler:
Show
The answer is 950 ppm, if you've done it correctly.
4. Legends.. Thanks both

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