Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: 2kool4u on March 02, 2008, 12:01:22 AM
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the question is:
you are provided an aqueous solution which is blue. Addition of dilute hydrochloric acid produces a precipitate. The precipitate dissolves when the solution is heated to boiling. What two cations were in the original solution?
plz any if u can help . i tried ... but cant get it ... hope someout outthier can. Thanks.
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Which cation is blue?
Which chloride is weakly soluble in cold water, but well soluble in hot water?
I don't like this question.
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Which cation is blue?
Which chloride is weakly soluble in cold water, but well soluble in hot water?
I don't like this question.
potassium chloride is the answer.at 0 degree centigrade is solubility is under 50g/100g and at 100 degree centigrade more the 50g/100g.its keep on increasing with increase in temperature and at around 300 degree centigrade it is more then 100g/100g.
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I can think of a better choice than shaziaahsan's, but the person with the best answer is Borek, this question is too general for a good answer. You should have some idea of what ions to expect. Is there any more to the question? See what your textbook says.
There are some, but not a whole lot of, hints we can give you to help you along. Beyond that you're called to memorize a small subset of the solubility and reaction rules for anions and cations, or follow a carefully planned flowchart.
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50g/100g is not weakly soluble.
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then for the help . ill follow the flow chart idea ... seems like a good one.
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Two cations are intensively blue in water solution, if you do not limit cations to the first two analytical groups.
Only one gives colourless chloride, which is soluble in hot water. Solubility of this salt is :
0.99 g / 100 g H2O at 20 C,
1.98 g . at 60 C
3.34 g . at 100 C
Of course, solubility can be lower at the presence of some excess (but not a big one) of HCl