Chemistry help #2
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21 Feb 2012, 15:49
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Journals
Yo fellas,
i thought there might be a chemistry owner on here and could help me...
so i need to get the pKs-value of HCL with c(HCL)=10^6
i know pH=-log(10^6)=6 so how can i get the pKs out of the pH=6??
i thought there might be a chemistry owner on here and could help me...
so i need to get the pKs-value of HCL with c(HCL)=10^6
i know pH=-log(10^6)=6 so how can i get the pKs out of the pH=6??
pKs=10^6:-log(10^6)
if i'm right :x
it must be between 1-4 and if i am right is the pks value of HCl around is 2 or 3
never trust wikipedia mate^^
no shit ? :P
pOH=14-pH
pOH=1/2*pkb - 1/2*logCob das nach pkb umstellst
und dann pks=14-pkb?
da ja HCl ne starke Säure ist würde ich diesen weg gehen, wäre es zum beispiel ne schwache säure dann wäre es izi
e: hmm wobei du kannst net sagen das pH=6 ist... da es sich um ne stark säure handelt kannst du net einfach die formel pH=-logCos benutzen sondern die formel pH=-log[H+], aber die konzentration von H+ Ionen kann man eigentlich NICHT berechnen wenn du nur Cos gegeben hast.
Kannst du irgendwie die ganze aufgabe scannen oder abschreiben?
irgendwie ist das ne tricky aufgabe :<
H+ *hust*
H3O+ *
[H+]=-Ks/2 + 1/2 * sqrt(Ks^2 + 4*Ks*Cos) weil du da 2 unbekannte hast :x
habe erst vor 3 wochen mei stöchiometrieprüfung geschrieben jetzt muss ich nur noch 7 tage auf meine ergebnisse warten omg :DDDDDD
c(hcl)=10^6 ist arg viel :P oder doch eher 10^-6 :P
In the first case you're supposed to deal with a solid.
wenn du nämlich 10^6 hast, dann ist dein ph sowieso falsch, da du ja pH=-log(10^6) --> pH =-6 hättest... ;)
just sayin
It can be used if [HCl]>10^-5mol/dm3 otherwise you may have bad results.
Anyway there's no problem in here.
H3O+ + Cl- => HCl + H2O
(The reaction is 99% this way since HCl is a strong acid so it's difficult to make it the other way <=. It also means that we have a proton in the solution and a very weak base Cl-)
"Ks" as you call it is supposed to be this way :
Ks = [H3O+][Cl-]/[HCl][H2O]
H2O activity is 1 nothing new...
So Ks = [H3O+][Cl-]/[HCl]
This reaction is more likely total that's why we consider :
[H3O+]=[Cl-]=[HCl]
Ks = 10^6
So pKs = -6
pKs is not pH obviously...
If we have a look at chemistry table for HCl it's supposed to be pKs<-1.74 so the result seems legit unless I did something wrong but I doubt.
?
as HCl is a very strong acid,we can assume, that pH=pKs due to the complete dissociation of the HCl molekule?
Could you please tell me that 3rd degree equation,just to see if we get tought the same =)
EDIT: oh and pls dont come up with that pKs-related formula to calculate the pH of acids since we have HCl,no doubt about being a very strong acid :s
Anyway : (H+)^3 + Ks (H+)^2 - (H+) [Ke + KsCs] - Ks.Ke = 0
Too lazy to do it...
Got Ks = 7,14285 × 10^-20
so pKs = -19 approximately
I have no idea what to think about it. All I know is the equation is correct and we can have negative pKs for strong acids.
Are you sure that you can use this equation for every acid in any concentration?
The result of your calculation make me doubt that coz pKs=-19 for HCl which is used by 1st semester students seems a bit heavy for me :D
und pKs=log[c(HCl)].
Gibt noch andere Rechenwege,aber solange du keine weiteren Angaben hast,sollte das die Lösung sein.
Und ich hoffe,du hast 10^-6 mol/L,anderfalls solltest du mal in Stockholm anrufen,hochkonzentrierte Salzsäure hat etwa 13 mol/L.