moedank (Stranger)
08-05-03 20:13
No 451842
       getting a 2M solution from 31.45% muriatic acid?  Bookmark   

i have a bottle of the pool shit and it is 31.45%.  I need a 2M solution of hydrochloric acid.

I kinda understand mole calculation, but i have no idea how to do it starting with a soultion of 31%.

Please help!  I have "dinner" on the stove and this is holding me back. 		 
 
 
 
    acid_egg
(Hive Addict)
08-05-03 21:08
No 451864
       2M= (HCl:g/mol) x 1L x 2(mol/L) = 36.46 x 1 x...  Bookmark   

2M= (HCl:g/mol) x 1L x 2(mol/L)
= 36.46 x 1 x 2 =72.9

1ml 31.5% HClaq=0.315g HClg

72.9/0.315 =231.42

therefore 231.42ml of your 31.5%HCl contains 79.46g HCl which will when diluted to 1L give a 2M soln.

[edit]ps this is a great little tool giving g/mol on molecular formulae and where I calculated the above ../rhodium /equipment/calculator.html 		 
 
 
 
    moedank
(Stranger)
08-05-03 22:03
No 451877
       thanks for the help! Thanks for that link too.  Bookmark   

thanks for the help!  Thanks for that link too. 		 
 
 
 
    acid_egg
(Hive Addict)
08-05-03 22:15
No 451879
       Whoa...hold up there just a sec I may have...  Bookmark   

Whoa...hold up there just a sec I may have made an error.
g/ml for HCl should have been calculated by W/W% x density/100 as shown in this post on ammonia soln. Post 276526 (WizardX: "Re: Q's On WizardX's H2S Meth", Stimulants) so ammend that 0.315g/ml by multiplying by density and calculate as above.

I would also be very surprised if your HCl is really 31.45% though.tongue 		 
 
 
 
    moedank
(Stranger)
08-05-03 22:52
No 451885
       god i should have listend in math class...........  Bookmark   

31.45% is what is says on the bottle.  Should i bee worried about it not meeting what the lable claims. 		 
 
 
 
    hypo
(Hive Addict)
08-05-03 23:04
No 451887
       geeeeez...  Bookmark   

you're making it more complicated than it is. looky:

conc. HCl (36%) is 6N. you want 2N? dilute it to a third: 1 part HCl, 2 part water.
maybe use 1.2 part HCl since you only have 31% (-20%). done.
can be done in your head in 20 seconds, has been discussed ad nauseum.

is this exact? no way. but if you need analytical exactness, you can't use
hw store HCl anyway. if you want to exactly neutralise you need an indicator
anyway. so there... 		 
 
 
 
    acid_egg
(Hive Addict)
08-05-03 23:44
No 451892
       Should i bee worried about it not meeting what  Bookmark   

Should i bee worried about it not meeting what the lable claims
No...but it's nice of them to give you the percentage to 2 decimal places on hardware HCL don't you think?wink

but if you need analytical exactness, you can't use
hw store HCl anyway

Hypo that's what I was implying, however there is no harm done in explaining how it should be worked out. 		 
 
 
 
    methyl_ethyl
(Hive Bee)
08-06-03 00:40
No 451899
       Oh Shit!!  Bookmark   

conc. HCl (36%) is 6N

     I really thought concentrated HCL was 12N.  Please correct me if I am wrong,  frown.   I may be unemployed soon.......  crazy
     Unipolar Mania, It's good for life... laugh 		 
 
 
 
    acid_egg
(Hive Addict)
08-06-03 00:49
No 451902
       good point!  Bookmark   

good point!wink

it is. 		 
 
 
 
    Aurelius
(Active Asperger Archivist)
08-06-03 00:52
No 451904
       Me_Et  Bookmark   

Methyl_Ethyl, you are correct.  Conc. HCl acid is 12.1M (also 12N)
Act quickly or not at all. 		 
 
 
 
    scram
(Hive Bee)
08-06-03 02:30
No 451934
       FYI: The d20 of that 31.45% in this region...  Bookmark   

FYI: The d20 of that 31.45% in this region used to be 1.148 		 
 
 
 
    neopharmaphobia
(Stranger)
08-06-03 06:18
No 451997
       HCl molarities and dilution
(Rated as: excellent) 		 Bookmark   

"Concentrated" HCl in the lab is generally accepted as a 37.3% solution, which is 12M. 31.45% is more like 10M.

A simple dilution formula from High School Chemistry, based on molarity, can be used:

C1V1 = C2V2

C = Concentration, V = Volume

In your case, if you wanted 1L of 2M soln.:

(10M)(V2) = (2M)(1L)

and solve for V2. It comes out to be .2L (200mL), use this much of your 10M solution and dilute it to 1L (add 800mL).
Easy, and you should know the molarity of your solution so you can do it simply in your head, as hypo says.

Here's a table of HCl % concentrations, and their corresponding densities and molarities.

Conc. (W/W)% Density (g/mL) Molarity (Mol/L)
1 1.0032 0.275
2 1.0082 0.553
4 1.0181 1.117
5 1.0230 1.404
6 1.0279 1.691
7 1.0328 1.984
8 1.0376 2.277
10 1.0474 2.872
12 1.0574 3.481
14 1.0675 4.100
16 1.0776 4.728
18 1.0878 5.370
20 1.0980 6.023
22 1.1083 6.687
24 1.1187 7.364
26 1.1290 8.050
28 1.1392 8.749
30 1.1493 9.457
32 1.1594 10.176
34 1.1691 10.902
36 1.1789 11.640
38 1.1885 12.386
40 1.1980 13.143
 
 
 
 
    moedank
(Stranger)
08-06-03 09:04
No 452033
       damn!  Bookmark   

I really didnt expect this much help.  I thank all of you for helping me out.  I am just starting my chemistry journey and yall helped out alot. 

thanks again and bee looking for my trans-4-mar(ice) write up. we will see if someone with hardly any knowledge of chem. can bee all he can bee.
meanest mother fucker in the valley