Calculating Ksp of Ag2CrO4 from Experimental Data

[Seinfeld4]

Homework Statement

Hi,

I need to calculate the Ksp of Ag2CrO4 based on experimental data.

During the experiment, 1.25g of pure copper was placed in a 1.00 L solution of silver chromate. When the copper was extracted, only 1.24g remained.
Balanced chemical equation: Cu + Ag2CrO4 --> CuCrO4 + 2Ag

The Attempt at a Solution

Here's what I did:

mole of copper = 0.01g / 63.546
= 1.57 * 10^-4

Since volume is 1.00 L, the number of moles is equal to the concentration.
There are 2 moles of Ag and 1 mole of CrO4 for every mole of copper, so:

Ksp = (1.57 * 10^-4) (3.15 * 10^-4) (3.15 * 10^-4)
= 1.56 * 10^-11

But this doesn't seem correct because the actual value is 1.1 * 10^-12.
This would give me a percentage error of over 1000%...

Any help would be much appreciated.

 

[Borek]

Your approach looks correct and the answer seems to be consistent with the data given.

I don't like this question. I wonder how they extracted the copper. Solid left after reaction completed should weigh more, not less.

 

[Seinfeld4]

Ok, I thought I was doing it properly. I'm not sure why they made a question that produced a % error greater than 1000. Anyways, thanks Borek!

 

[Liquity]

I'm currently working on this same question, lol, can you tell me if the answer to this question was marked correctly? I got the same answers with the same approach.. I know this thread is a year old ._.

 

[DeeNos]

I would first check the accuracy of the experimental data and the assumptions made in the calculation. It is important to ensure that the mass of pure copper used and the mass remaining after the reaction were measured accurately. Additionally, the assumption that all of the copper reacted with the silver chromate may not be completely accurate, as there could be other factors at play such as impurities or side reactions.

Assuming the experimental data is accurate, I would suggest rechecking the stoichiometry of the balanced equation. It appears that the number of moles of Ag and CrO4 used in the calculation may be incorrect. It may be helpful to double check the coefficients in the equation and make sure they are correctly accounted for in the calculation.

If the stoichiometry and experimental data are accurate, the discrepancy between the calculated and actual value could be due to experimental error or limitations of the assumptions made in the calculation. I would suggest repeating the experiment and/or using alternative methods to confirm the accuracy of the results. Additionally, it may be helpful to compare the calculated value to other published values for Ksp of Ag2CrO4 to determine the level of agreement.

In summary, as a scientist, I would recommend thoroughly checking the accuracy of the experimental data and assumptions before drawing any conclusions about the calculated Ksp value.