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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Rayan on June 07, 2005, 05:09:04 PM

Title: conductivity
Post by: Rayan on June 07, 2005, 05:09:04 PM

we had this question in our exam:
 
conductivity distilled water = 0
                 distilled water + sugar = 0  
                 distilled water + HCl = 11
                 distilled water + CH₃COOH = 5

(i'm not sure of the 5 and 11 but there was a difference, not so very big between the two values.)
we were asked to comment on these given.
i thought that: the conductivity is due to movement of ions. in distilled water there are no ions thus no electron transfer => cond. = 0
when we add sugar, no ions will dissociate into water, thus we also have no electron transfer => cond. is 0.
in the HCl case, the acid will dissociate and give H⁺ and Cl^- and we'll have ions moving electron.
and for CH₃COOH, we'll also get H⁺ and CH₃COO^- . but can we conclude that  the conductivity of CH3COO^- is less than that of Cl^- because of the difference in conductivities?
and is my analysis is correct from the begining?

Title: Re:conductivity
Post by: savoy7 on June 07, 2005, 05:44:35 PM

think about the difference between strong and weak acids.

HCl is a strong acid
Acetic acid is weak

The answer can be found there.

savoy

Title: Re:conductivity
Post by: Rayan on June 08, 2005, 03:59:16 AM

then the difference in condictivities is because the strong acid dissociates completely while the weak acid dissociates partially in water.

Title: Re:conductivity
Post by: ksr985 on June 08, 2005, 12:26:58 PM

yup. there will be a greater number of ions in the HCl soln, than in the CH3COOH soln, assuming the molarities of the two to be the same.

Title: Re:conductivity
Post by: arnyk on June 09, 2005, 06:35:56 PM

The higher the ionization of an acid, the more conductive it will be (because there will be more ions in the solution).  So what does that say about the level of ionization of strong acids as opposed to weak acids?