What will you be doing over the Easter break? >>

working out units for a rate equation...

Can you explain how you get to the final units please? :redface:

mol dm-3 s-1
---------------
(mol dm-3)^2 (mol dm-3)

Cancelling down you get: mol-2 dm6 s-1

I kinda get the basics, divide things with indices and you subtract them and when you multiply you add them.. And if somethings on the top and bottom they cancel each other out. But this is getting a bit beyond me :redface:

I know where the s-1 is from but I don't understand why its -2 and not +2? and vice versa for the 6.

please help :smile:

Reply 1

forkwise

it cancels to

s^-1
......................
(mol dm^-3)^2

s^-1
....................
mol^2 dm^-6

so it's s^-1mol^-2dm^6

Reply 2

Aired

mol dm-3 s-1
---------------
(mol dm-3)^2 (mol dm-3)

Sort out the bottom line first:

(mol dm-3)^2 (mol dm-3) = (mol dm-3)(mol dm-3)(mol dm-3)

= (mol dm-3)(mol^2 dm -6)

= mol ^3 dm^-9

So now you've got...

mol dm^-3 s^-1
-------------
mol ^3 dm^-9

= mol^-2 dm^6 s^-1

Reply 3

Nez

moldm-3s-1/moldm-3 moldm-3 moldm-3
cancels out to
s-1/moldm-3moldm-3 = s-1/mol2dm-6
but to make it easier u sort of flip the bottom bit to the top by switching the signs so

s-1/mol2dm-6 becomes mol-2dm6s-1

dunno if that makes any sense