Is it me or is this question inane

[chiddler]

---

Members don't see this ad.

The Ksp value for which of the following salts is the MOST accurate in terms of smallest percent error?

Answer: The salt with the largest solubility, because if you can dissolve more salt you have an easier time measuring it. "As a general rule, the larger the value, the less significant the error in its measurement."

Like I wrote in the title, this question seems useless and irrelevant. Am I right or am I missing the point of this question?

Danke.

 

[SaintJude]

I agree & seems to me a very unlikely question to appear on the MCAT. What test prep source is this question from
?

 

[chiddler]

I agree & seems to me a very unlikely question to appear on the MCAT. What test prep source is this question from
?

berkeley review

older version. not sure what year, though, because the book has no year in it

 

[MedPR]

The Ksp value for which of the following salts is the MOST accurate in terms of smallest percent error?

Answer: The salt with the largest solubility, because if you can dissolve more salt you have an easier time measuring it. "As a general rule, the larger the value, the less significant the error in its measurement."

Like I wrote in the title, this question seems useless and irrelevant. Am I right or am I missing the point of this question?

Danke.

I think it's a valid question. There is a section in TBR that mentions different methods of measuring solubility and how weighing the precipitate only works for very insoluble solutes.

Imo this is just another convoluted mcat concept question that is good to wrap your head around just in case.

 

[Ssina]

I think it's a valid question. There is a section in TBR that mentions different methods of measuring solubility and how weighing the precipitate only works for very insoluble solutes.

Imo this is just another convoluted mcat concept question that is good to wrap your head around just in case.

I've seen couple of WIERD questions like that on the AAMCs also.... I don't like it either personally, but nonetheless, they show up!

 

[Erythropoietin]

The Ksp value for which of the following salts is the MOST accurate in terms of smallest percent error?

Answer: The salt with the largest solubility, because if you can dissolve more salt you have an easier time measuring it. "As a general rule, the larger the value, the less significant the error in its measurement."

Like I wrote in the title, this question seems useless and irrelevant. Am I right or am I missing the point of this question?

Danke.

This is a simple question but it just requires that "aha!" moment.
Anyways, I think of it this way:
Say you are a beginner at baseball. The more days (larger value) you practice, the more you improve. Less days you practice, and less likely you improve. After a while when you are about to take the game-winning shot, you will more likely to hit the ball well if you trained well (hence, smaller percent error of missing the shot). Conversely, if you train less you will have a higher chance of missing it (higher percent error). Anyways I'm sure there are other bunch of examples to relate to this.
So in terms of salts, look at the molar solubility and consider which dissolves the most. The more you dissolve, the better you are able to measure % error and the smaller it will be.

 

[MedPR]

You can also think of it in terms of impurities in the solvent. If you assume there are 5mol impurities in the solvent, and you are able to dissociate 50mol of salt A but only 10 mol of salt B, the calculations for salt A will be less affected by the 5mol of impurities since there is so much more salt dissociated.

 

[MT Headed]

I don't like either of the two approaches above me. I think the point they were trying to make is that you typically have a measuring device that measures to some precision, say 0.1g.

With a highly insoluble salt, you might dissolve 0.4g in a liter of water before it starts precipitating. Well, this is a measured value, so it's really somewhere between 0.35g and 0.45g per liter.

Now take a highly soluble salt. Now you might measure 4012.2g dissolved before it starts precipitating. Again it is a measured value so the true value must lie somewhere between 4012.15g and 4012.25g.

Which measurement is most accurate, i.e. has the smallest percent error?

This question distracts you with Ksp but it is really trying to get you to think about significant figures, rounding, etc. This is an important scientific concept and usually covered in the first lab of gen chem when nobody knows what is going on. I kind of like the question, actually.

 

[chiddler]

thanks for the responses. I understand the question and the answer so i don't need help with that, thanks.