Ppm, equations, atmosphere/molecules help?

• Chemistry

Homework Statement

At sea level, there are approximately 2.6 × 1025 molecules m-3 of the atmosphere.
One of the gases making up the atmosphere has a concentration of 3.90 × 1021 molecules m-3. What is the concentration of this gas expressed in parts per million (ppm)?

The Attempt at a Solution

totally flumoxed once again lol

2.6x1025 - 3.90x1021 = 2.59961x1025

now the answer is wrong, what i have done is wrong and to get the right answer in ppm is completely going over my head for some stupid reason.

Cheers Emma

Borek
Mentor
Can you give answer in %?

nope tried even that is escaping me

how do i get it into %?

39ppm?

Borek
Mentor
No.

What is definition of % concentration? ppm is very similar, just instead of multiplying by 100% multiply by 106ppm.

This can be a little bit tricky, as you have to calculate ppm in terms of molecules/molecules, while usually we do it mass/mass or something like that. But other than that it is not different.

ok so why multiply by 106?

I just dont get it?

sorry being extra thick today

emz

Borek
Mentor
What is definition of % concentration?

to be perfectly honest i just have no idea.

Borek
Mentor
But you do have a book or notes or at least access to internet, and you know how to use google?

helpmz2011
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