PDA

View Full Version : solubility of several substances

chemist2b
Dec19-11, 06:22 PM
are these soluble in water?

Na2Cr2O7 (i think yes)

(NH4)2Cr2O7 (i think yes)

PbCr2O7 (i think no)

CuI2 (no? whay is this disproving by rule that iodides and chlorides are soluble in water except for heavy metals?)
chemisttree
Dec20-11, 01:26 AM
Maybe copper is a heavy metal?
Borek
Dec20-11, 02:39 AM
CuI2 (no? whay is this disproving by rule that iodides and chlorides are soluble in water except for heavy metals?)

There is no such compound, so it is hard to say if it is soluble.

This is a very specific case.
chemist2b
Dec20-11, 11:09 AM
so this was the equation i was given: KI + CuSO4---> something

i assumed it was k2S04 and CuI2

this is supposed to be either no reaction or double repleacement

maybe having the whole equatoin helps?

but the other three were correct, right?
Borek
Dec20-11, 02:13 PM
this is supposed to be either no reaction or double repleacement

Actually it is neither. And it is really not that difficult to check, some googling should help you quite fast.

but the other three were correct, right?

Yes.
chemist2b
Dec20-11, 05:46 PM
so if i cancel out spectators, it is a synthesis reaction (most sites agree that cuI2 is insoluble in water)

Cu +2 (aq) + 2I -1(aq) ---> CuI2 (s)

what i dont understand is why it is disproving my solubility rule (iodides are insoluble except for heavy metals, and copper isn't a heavy metal).

ps. you can be awful at googling. if i was good at it i would probably not have to ask these questions here.
:(
Borek
Dec21-11, 02:19 AM
Show me one site that lists CuI2 as insoluble.
chemist2b
Dec21-11, 11:19 AM
hte site of the sheet that my teacher gave me. it says "ss" for slightly soluble which he told us to assume meant insoluble. but i gues the chart isnt that reliable. because llokibng now at the other ones i see mostly blanks but one or two say soluble. thanks...
Borek
Dec22-11, 01:50 AM
hte site of the sheet that my teacher gave me. it says "ss" for slightly soluble which he told us to assume meant insoluble. but i gues the chart isnt that reliable. because llokibng now at the other ones i see mostly blanks but one or two say soluble. thanks...

Are you sure it shows solubility of copper(II) iodide and not solubility of copper(I) iodide?

In water solutions in the presence of iodides copper(II) oxidizes iodides to iodine and gets reduced to copper(I), this is followed by copper(I) iodide precipitation. CuI is weakly soluble, CuI2 doesn't exist.