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Oregon State University Ecampus Online Chemistry Lecture - Spectator Ions

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Hi, I have a beaker of plain de-ionized water and a solution containing some potassium-iodide, and I will show you the formula and reaction up on the board in a moment, and some lead-nitrate. Both of these are clear solutions. Since this one contains the iodide we usually put it in a brown bottle because iodide is photo-chemically active. Some light will go ahead and make it change over time so we put it in a tinted bottle. I just put a little bit of that in. And watch this...this is a nice reaction. We form a solid precipitate. A yellow solid it formed. Over time it will crash down to the bottom of this beaker. It is lead-iodide, which is very heavy, so it will sink down into the bottom of the beaker. Let me show you the net-ionic equation and the overall reation. I added a solution of lead-nitrate, I have it correctly labeled as ageous because all nitrates are soluble. Nitrate is a spectator ion-it doesn't do chemistry. If you think of it, it's a way of getting lead into solution. The other solution contains potassium-iodide and all potassium salts because potassium in group one are soluble. So this is correctly labeled ageous solution. Now what's going to happen when these things are mixed, the spectator ions nitrate and iodide, sorry, nitrate and the potassium plus will absolutely nothing. They will continue to float around in the solution. But the lead 2 plus and the I minus will get together and make a precipitate. A solid. The yellow solid that goes down to the bottom of the beaker. So I wrote up here a couple of potassium-nitrates and this is just to balance the reaction. I correctly have it shown as ageous. Meaning they are dissolved, floating around in solution. But this is your solid. Our net-ionic equation, meaning do not include the spectator ions does not involve nitrate or potassium plus. So the net-ionic equation or NIE contains lead 2 plus, lead 2 plus is ageous at the beginning because it was combined with the nitrate. It is two plus because each nitrate is minus one. It gets together with a couple of iodides. The iodides are ageous, they are floating around in the solution. they were put in there with potassium but now they get together and form the solid PBI2S, the solid lead-iodide.

Video Details

Duration: 2 minutes and 40 seconds
Country: United States
Language: English
Genre: None
Views: 109
Posted by: umarket on Sep 24, 2009

Videos were taken from an Online Chemistry course provided by Ecampus at Oregon State University. The professor is Dr. Richard Nafshun.

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