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akcapr

qucik question

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on this state test we were taking there was a lot of controversoy about the right answer for this simpele question but somehow not so simple:

 

what metal reacs in the closest manner with copper sulphate solution as mg does?

 

A. aluminum

B.Calcium

C sodium

D potassium

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wow. you could argue many different answers there.

However, I believe it would be Calcium because they are in the same group.

It is a poorly worded question

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I'd agree its the only other group two metal there.

 

~Scott

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This is where I would disagree and state that the answer is aluminum. In both cases, the Mg and Aluminum would replace the copper ions in solution forming copper metal and an ionic solution of metal ions and sulfate ions. Calcium, potassium, and sodium would all react with the water in the solution instead of the ions, forming calcium/sodium/potassium hydroxides in preference to the sulfates.

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If the question was 'what forms the compound closest in manner to magnesium?' then it would be calcium. But the question states 'what reacts with copper sulfate similar to magnesium?'.

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thx. I thin kthey were looking for the answer Ca.

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jdurg, you're forgetting that the alkali/alkaline earth hydroxides would react with cupric sulfate, forming cupric hydroxide and the alkali/alkaline earth sulfate

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Yes, but that is only after the formation of the hydroxide. Therefore, that would be a reaction between the alkaline earth hydroxide and the copper sulfate. Magnesium metal will not react with water unless it's in the form of steam. If you put a piece of aluminum into a beaker of CuSO4, a piece of magnesium into a beaker of CuSO4, a piece of calcium into a beaker of CuSO4, a piece of sodium into a baker of CuSO4, and a piece of potassium into a beaker of CuSO4, the reaction of the aluminum and the magnesium would be nearly identical. The reactions involving Ca, Na, and K would be quite a bit different (And a little bit more violent). :D

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well the Ca, Na and K would react with the CuSO4, just indirectly. plus, who says we're doing this reaction wet or in water? we could be thermiting. we could be doing this in pyridine, etc.

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Because it's a state exam and says 'copper sulfate solution'. Copper sulfate solution generally implies 'in water' as I'm pretty sure that CuSO4 doesn't have any appreciable solubility in non-polar solvents. (As it's barely even soluble in ethanol). In order for it to be a thermite, you couldn't have the reaction in a solution as the initial question implies. We also know that it's not molten CuSO4 as the question again asks for reaction in solution. Therefore, you can conclude that this is a water solution.

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yeah, i didnt read everything.

 

while the monohydrate is almost completely insoluble uin ethanol, the pentahydrite is soluble in methanol, glycerol and somewhat soluble in ethanol. but since it is a state exam, i understand.

 

nonetheless, i reiterate: for all intents and purposes, the K, Na and Ca react with the CuSO4. the hydroxides are only present for a fraction of a second (unless the cupric sulfate is really dilute) before you get the MSO4 or M2SO4 and Cu(OH)2

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