QUick QuestioN!!

[man0005]

Can someone explain to me what the unit gm/L is? regarding density
and whats the formula relating to density?

[Mint]

Density is m/v

[man0005]

whats gm?

[pi]

Sure its not g/mL instead?

[man0005]

it says gmL^-1 :S

i'll give you whole question, easier for everyone

The concentration of ethanol (C2H5OH) in a sample of Brandy is 4.8 M (mol/L). If the density of ethanol is 0.79 gmL^-1 , calculate the concentration of ethanol % (v/v) in the Brandy. (Assume 20 mL of Brandy)

[pi]

That means g/mL  (think of it as g(mL)^-1)...

[man0005]

oh really?
do they normally capitalise the L at the end? O_O
so confusing

[chuck_norris]

Yep L = litres and m is the milli prefix (1/1000)

So mL = 1 milli litre

It's not proper notation, as just gmL^-1 but it is so common that the parenthesis are left off.

But density is a measure of the mass per unit volume - the higher the density, the more "concentrated" or compact the substance is.

[man0005]

oh okay
thanks for that guys

[man0005]

if you guys have time, can you try the question and tell me what you get, so i can see if i did it right

[chuck_norris]

The concentration of ethanol (C2H5OH) in a sample of Brandy is 4.8 M (mol/L). If the density of ethanol is 0.79 gmL^-1 , calculate the concentration of ethanol % (v/v) in the Brandy. (Assume 20 mL of Brandy)









(this is not a frequently used formula, but with stuff like this just look at the units - you have g and gmL^-1 and you want to end up with mL only so you go -- where v=volume; m=mass; d=density.)

So, as a percentage that is:

%% (2sf)

[man0005]

awesomeee, got the same
thanks for that

[chuck_norris]

No worries, man0005.