quick question on chemistry

[grami001]

________ _Ksp_________________

AgSCN 1.0 x 10 -12

Ag2CrO4 9.0 x 10 - 12

Ag2SO3 1.5 x 10 -14

Use the foregoing data to determine the order for the molar solubility of the salts.
a. Ag2CrO4 > Ag2SO3 > AgSCN
b. Ag2CrO4 > AgSCN > Ag2SO3
c. AgSCN > Ag2CrO4 > Ag2SO3
d. AgSCN > Ag2SO3 > Ag2CrO4
e. Ag2SO3 > Ag2CrO4 > AgSCN

The answer is A. I know that you have to count the ions but that is not necessarily true in every case. It just happened that it worked out in this problem. Do you guys know an exact way to find the answer besides counting ions.
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[PreDent2009]

The larger the Ksp the more soluble the compound is. So in terms of negative exponents you want the number to be closer to 1.

 

[osimsDDS]

how does that make sense? if you have a higher Ksp it would be more soluble so shouldnt Ag2SO3 have the lowest molar solubility since it has the lowest Ksp? The answer is A showing that it is in the middle but shouldnt it be B where Ag2SO3 has the least molar solubility because it has the lowest ksp??? someone please explain

 

[doc toothache]

________ _Ksp_________________

AgSCN 1.0 x 10 -12
Ag2CrO4 9.0 x 10 - 12
Ag2SO3 1.5 x 10 -14

Use the foregoing data to determine the order for the molar solubility of the salts.
a. Ag2CrO4 > Ag2SO3 > AgSCN
b. Ag2CrO4 > AgSCN > Ag2SO3
c. AgSCN > Ag2CrO4 > Ag2SO3
d. AgSCN > Ag2SO3 > Ag2CrO4
e. Ag2SO3 > Ag2CrO4 > AgSCN
​

In AgSCN Ksp= [Ag+][SCN-]; [AgSCN]= 1 x 10-6
In Ag2CrO4 Ksp=[2Ag+]2 [CrO4-2]; [Ag2CrO4]= 7.5 x 10-5
In Ag2SO3 Ksp = [2Ag+]2 [SO3-2];[Ag2SO3]= 6.165 x 10-6

 

[Hunt Texas]

The answer should be B. As far as calculations go, i'm not sure how you got those concentrations b/c the question only gives you Ksp and no other conc. The larger the Ksp, the larger the molar solubility.

 

[osimsDDS]

The answer should be B. As far as calculations go, i'm not sure how you got those concentrations b/c the question only gives you Ksp and no other conc. The larger the Ksp, the larger the molar solubility.

yea iam wondering the same exact thing you are..

 

[klutzy1987]

where is this question from. Is it possible there is a mistake???

 

[doc toothache]

The answer should be B. As far as calculations go, i'm not sure how you got those concentrations b/c the question only gives you Ksp and no other conc. The larger the Ksp, the larger the molar solubility.

There is no mystery in the calculations. Given a Ksp you can find the molar solubilities of the component ion/anion. The comment on the larger Ksp and solubility holds true if you are comparing monovalent ions/anions. It does not hold true if trying to compare mono with divalent or multivalent and thus the need for calculations.

For AgSCN, Ksp= [Ag+][SCN-]; [AgSCN]= 1 x 10-6
For Ag2CrO4, Ksp=[2Ag+]2 [CrO4-2]; [Ag2CrO4]= 7.5 x 10-5
For Ag2SO3, Ksp = [2Ag+]2 [SO3-2];[Ag2SO3]= 6.165 x 10-6

where is this question from. Is it possible there is a mistake???

Mistakes are always possible, but this is not one of them.

 

[klutzy1987]

oops lol i misread the question. I thought the top equation was choice A i didnt pay attention to the answer choices on bottom. I should have read the question more carefully. I thought he was asaying that the top equation was fastest and i didnt see why.

 

[doc toothache]

oops lol i misread the question. I thought the top equation was choice A i didnt pay attention to the answer choices on bottom. I should have read the question more carefully. I thought he was asaying that the top equation was fastest and i didnt see why.

Rate (speed) is not involved in Ksp.

 

[osimsDDS]

In AgSCN Ksp= [Ag+][SCN-]; [AgSCN]= 1 x 10-6
In Ag2CrO4 Ksp=[2Ag+]2 [CrO4-2]; [Ag2CrO4]= 7.5 x 10-5
In Ag2SO3 Ksp = [2Ag+]2 [SO3-2];[Ag2SO3]= 6.165 x 10-6

I might be mistaken but i believe you numbers for Ag2CrO4 and Ag2SO3 are incorrect...it is basically Ksp = 4x^3 for both of those...you divide by 4 and then take the square root of the 3rd power or basically to the power of 1/3...so the answer should be...

AgSCN=1 x 10^-6
Ag2CrO4= 1.3x10^-4
Ag2SO3= 1.6x10^-5

 

[kkatranji]

I still don't understand this question...

The question asks you to rank the molar solubility of the salts (both ions together) and they give you the ksp for the salts.

why do you rank them according the solubility of the individual ions....?

This is exactly why I am bad at chemistry.

 

[doc toothache]

I might be mistaken but i believe you numbers for Ag2CrO4 and Ag2SO3 are incorrect...it is basically Ksp = 4x^3 for both of those...you divide by 4 and then take the square root of the 3rd power or basically to the power of 1/3...so the answer should be...

AgSCN=1 x 10^-6
Ag2CrO4= 1.3x10^-4
Ag2SO3= 1.6x10^-5

Thanx. You are right. Where is a good calculator when you need it? Or in the absence, be able to do simple math.

 

[Predentknight]

So final answer B? this seems to be a fairly simple problem no?

 

[osimsDDS]

no its still answer A....10^-6 is the smallest, least soluble, while 10^-4 is the biggest...most soluble

 

[doc toothache]

I still don't understand this question...
The question asks you to rank the molar solubility of the salts (both ions together) and they give you the ksp for the salts.
why do you rank them according the solubility of the individual ions....?
This is exactly why I am bad at chemistry.

AgSCN = Ag+ + SCN-
1 mole...1 mole...1 mole