Topic: Purple fumes from yellow lead iodide and potassium nitrate mixture. (Read 5961 times)

Fmeub · « **on:** February 10, 2009, 01:18:02 PM »

The students mixed the following white powders: Pb(NO₃)₂ and KI in a test tube.Upon shaking the mixture yellow PbI₂ and KNO₃ formed. The students were supposed to stop the reaction there, but some bright sparks decided to heat the mixture.
Upon heating purple fumes were released and the yellow mixture became interspersed with grey bits, the overall color changed to beige with a slight orange glow.

Could someone please tell me what reaction(s) occurred upon heating this mixture?

nj_bartel · « **Reply #1 on:** February 10, 2009, 01:43:21 PM »

Decomposition product to iodine gas would be my guess for the purple fumes. The solid might be something like PbO₂, PbO mixture.

macman104 · « **Reply #2 on:** February 10, 2009, 01:47:33 PM »

That would be my guess as well.

Fleaker · « **Reply #3 on:** February 10, 2009, 02:29:18 PM »

Perhaps look in the CRC for the decomposition temperature of lead iodide.

It will be less than that of PbCl₂.

I'm assuming that all of the solution evaporated off and you were left with a mixture of PbI₂ and KNO₃.
Heating this further would cause some redox reactions to occur, most probable being the formation of lead oxides, KNO₂, and NO_x.

Topic: Purple fumes from yellow lead iodide and potassium nitrate mixture. (Read 5961 times)

Fmeub

Purple fumes from yellow lead iodide and potassium nitrate mixture.

nj_bartel

Re: Purple fumes from yellow lead iodide and potassium nitrate mixture.

macman104

Re: Purple fumes from yellow lead iodide and potassium nitrate mixture.

Fleaker

Re: Purple fumes from yellow lead iodide and potassium nitrate mixture.

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