grepfla
Harmless
Posts: 2
Registered: 16-12-2009
Member Is Offline
Mood: No Mood
|
|
HCl in IPA
For some fun I decided to make my own HCl IPA solution today. I Bubbled anhydrous HCl gas into anhydrous IPA.
After I was finished I weighed 30mL of anhydrous IPA which weighed 24.035g and 30mL of IPA/HCl which weighed 25.346g. This comes out to a little more
than 5% HCl by volume. Now this is according to the math I have done. However I have trouble calculating Normality or molarity of the solution.
Would this solution be about .12N or .13N?
|
|
|
User
Hazard to Others
Posts: 339
Registered: 7-11-2008
Location: Earth
Member Is Offline
Mood: Passionate
|
|
Oke my mathematics sucks but here goes.
1 mole of HCl weighs : 36,46 grams (wiki)
You have 1.311 grams of HCl (25.346-24.035)
So that is 0.0360 mole HCl (1.311 / 36.46)
That means there is 0.0360 mole in 30 ml
30ml | 1L
0.0360 | X
1 / 0.030 = 33.3333333
0.0360 * 33.333333 = 1.2
So that is ~1.2 moles per litre.
Can anyone check this.
I wouldn't want to give this poor fellow the wrong answer.
[Edited on 17-12-2009 by User]
What a fine day for chemistry this is.
|
|
|
Arrhenius
Hazard to Others
Posts: 282
Registered: 17-8-2008
Location: US & A
Member Is Offline
Mood: Stochastic
|
|
Looks right, though the 1/0.030 is confusing. What is this? You should include units in calculations (dimensional analysis) so you can check your own
work. A really easy way to do molarity calculations is to remember that mMol/ml = mol/L, so here one should quickly see 0.036mol = 36mmol.
36mmol/30ml = 1.2N (or molar... I always say N for acids).
|
|
|
grepfla
Harmless
Posts: 2
Registered: 16-12-2009
Member Is Offline
Mood: No Mood
|
|
Thanks
Ok that shows my math was almost right. I left out a place after the decimal, I believe with the .030 mess. I totally forgot about using mmol. I will
remember that next time Arrhenius. Thank you both very much. This is my first time posting here, its a great site and the only good legit chem site I
could find.
|
|
|
User
Hazard to Others
Posts: 339
Registered: 7-11-2008
Location: Earth
Member Is Offline
Mood: Passionate
|
|
Its a crosstabel ( no idea if this is the right word in english)
It's just a very graphic conversion method.
Factor?
|----------|
30 ml - 1L
0.0360 - X
|----------|
Factor?
Maybe this makes more sense.
The question here is : what is the factor between 30ml and 1L ?
If this factor is obtained by simply dividing the numbers, the same factor can be applied to the bottom.
If 30ml equals 0.0360 mol how many moles equals 1L?
Very simple material, maybe iam just confusing now.
[Edited on 17-12-2009 by User]
What a fine day for chemistry this is.
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
1.311 gm HCl x (1/36.46) moles HCl/gm HCl = 0.036 moles HCl
0.036 moles HCl x (1/30) 1/mL x (1000)mL/Liter = 1.2 moles HCl/Liter
Notice how the units cancel. If you write it out so that the dimensions are correct at the end, you will rarely make a mistake, if you can do
arithmetic.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
