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.

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

1ml 31.5% HCl_aq=0.315g HCl_g

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

https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/calculator.html

thanks for the help!  Thanks for that link too.

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 (missing)

(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.

31.45% is what is says on the bottle.  Should i bee worried about it not meeting what the lable claims.

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...

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?

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.

conc. HCl (36%) is 6N

     I really thought concentrated HCL was 12N.  Please correct me if I am wrong,    .   I may be unemployed soon.......   

good point!

it is.

Methyl_Ethyl, you are correct.  Conc. HCl acid is 12.1M (also 12N)

FYI: The d20 of that 31.45% in this region used to be 1.148

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.