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# Concentration in the format xM?

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1. Hi there! This may sound like a stupid question but it's something I've never been taught. I need to know this for Physics.

When given a concentration in the format 0.5M (0.5 is just an example), what does it actually mean? It's 0.5, but out of what? A litre? A decimetre cubed? Is it in moles?

Thanks!
2. (Original post by JustJusty)
Hi there! This may sound like a stupid question but it's something I've never been taught. I need to know this for Physics.

When given a concentration in the format 0.5M (0.5 is just an example), what does it actually mean? It's 0.5, but out of what? A litre? A decimetre cubed? Is it in moles?

Thanks!
It's just a shorthand way of writing mol dm-3 , known as the molar ratio between the moles of solute per dm3
So 0.5M = 0.5 mol dm-3

I also remember wondering what it was and just being puzzled by it

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