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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Wermol on July 03, 2005, 07:27:33 PM

Title: 6N HCl <-whats "N"
Post by: Wermol on July 03, 2005, 07:27:33 PM
Sorry for this very novice question, but what is 6N HCl, as a percentage. I've tried searching for the answer but there is really nothing to search for, I mean "N" is a pretty common term  :P. Is it just moles per liter thus 22% HCl?
Title: Re:6N HCl <-whats "N"
Post by: Mitch on July 03, 2005, 07:31:19 PM
N stands for Normal as M stands for Molar. For the case of 6N HCl, it is chemically equivalent to 6M HCl.
Title: Re:6N HCl <-whats "N"
Post by: Dude on July 04, 2005, 03:05:11 PM
Normality will always equal molarity for monoprotic (ones that donate one proton) acids.  Polyprotic acids (ie H2SO4) will have a different normality from molarity.  To get % HCl by mass, you will need to know the density, which I approximated as 1.2 in this example.  For a rigorously accurate answer, look up the actual density in something like an Aldrich catalog or CRC.  It looks like the value will around 20 %, as you answered.

(6 moles HCl / L)(36 g HCl/1 mol)( 1 L / 1200 g sol)

Title: Re:6N HCl <-whats "N"
Post by: Borek on July 04, 2005, 05:12:17 PM
Sorry for this very novice question, but what is 6N HCl, as a percentage. I've tried searching for the answer but there is really nothing to search for, I mean "N" is a pretty common term  :P. Is it just moles per liter thus 22% HCl?

Normality:
http://www.chembuddy.com?left=concentration&right=normality (http://www.chembuddy.com?left=concentration&right=normality)

Conversion (percentage to molarity, solve 10.8 for c%w/w):
http://www.chembuddy.com?left=concentration&right=percentage-to-molarity (http://www.chembuddy.com?left=concentration&right=percentage-to-molarity)

Or just use CASC:

19.9304%  ;)

Title: Re:6N HCl <-whats "N"
Post by: pkothari13 on July 04, 2005, 05:32:48 PM
as a side question, what would be the use of using Normality over Molarity? molarity is much more prominent and easier to work with. any thoughts???
Title: Re:6N HCl <-whats "N"
Post by: lemonoman on July 04, 2005, 05:47:33 PM
Since Normality equal to the molarity times the number of equivalents per mole of solute, normality is (theoretically) easier to work with for things like titrations, etc where equivalents are important.

Like, 10 mL of 0.1 M HCl (0.001 mol) needs 10 mL of 0.05 M Ca(OH)2 - which is 0.1 N with respect to OH- - this way, the numbers work better.

Of course, sometimes it's easier the other way.  It's like temperature.  Celsius, Kelvin, Fahrenheit, Rankin...Why don't we just use one eh  :P?
Title: Re:6N HCl <-whats "N"
Post by: Borek on July 04, 2005, 05:54:04 PM
as a side question, what would be the use of using Normality over Molarity? molarity is much more prominent and easier to work with. any thoughts???

Not necessarilly. If you have a solution that will be used for some kind of reactions it is sometimes easier to do the calculations expressing concentration not in molarity but in some other, sometimes exotic units. For example 1mL of titrant can be equivalent to 12.34 g Cl- per litre of brine - and I have seen such solutions in use in industrial lab in eighties (although I can't remember what was determined and I made this brine example).

These are all ways to facilitate calculations, that's all.