displacement reactions copper xmas tree & Ag N03?

Ocean Breeze · Post by **Ocean Breeze** » 22 May 2007, 12:10

The teacher wants to do a demo in afew days... cut a xmas tree shape out of Cu foil, and dip it in silver nitrate soln. Then its placed in the light and somethings supposed to happen. Thats all the info that I have been given. Help please.. anyone done this one? Any tips etc. I only have time (not even that) to trial it once, so any tips from those whove done it would be gratefully recieved.

ALSO just been asked if we can do the steel wool in a beaker one, where you pour in hot Cu SO4 soln. Not sure whats supposed to happen.

Lyn · Post by **Lyn** » 22 May 2007, 13:07

Rainbow-sky,

There are some times when you just need to provide the equipment asked for and let the teacher go. If a teacher is worth their salt they will trial the practical themselves beforehand.

The warm copper sulfate and steel wool practical is a good one. You can trial that one with a cold copper solution on steel wool to get a general idea. Its quick, easy and fun. Warming the copper solution before adding only speeds the reaction. I won't tell you the results. Sometimes it is nice to be surprised.

Lyn.

Alice · Post by **Alice** » 22 May 2007, 13:29

Hi Rainbow-sky

The copper X-Mas tree in Silver nitrate works well. It will grow silver crystals if left in the solution. (0.1M)

Down side is it will stain skin black, so wear gloves.

Also, Silver nitrate is expensive. We usually wind copper wire around a pencil, remove coil from pencil and suspend in a test tube of Silver nitrate. You can watch the silver crystals forming.

I agree with Lyn, staff should try out their own demos.

Alice

Ocean Breeze · Post by **Ocean Breeze** » 22 May 2007, 13:46

Alice & Lynn... thanks for your responses. I seem to be the one to be left to try out things.....especially cutting out a copper christmas tree! So do I leave the Cu in the Ag NO3 soln, rather than take it out? Teach said something about we put it in the light to react? RS

nickyw · Post by **nickyw** » 22 May 2007, 15:01

Hi Rainbow Sky

The Xmas tree prac is illustrated on the following web site:

http://genchem.chem.wisc.edu/demonstrat ... _trees.htm

I hope that helps you.

Cheers Nicky

Ocean Breeze · Post by **Ocean Breeze** » 23 May 2007, 09:34

Thanks Nicky.. very helpful.

Post by **Robb** » 23 May 2007, 14:13

Hi All,

Another reaction that could be done is a Reduction Reaction..

This can be also used as a displacement reaction due to the fact that Copper Oxide and Carbon powder (Activated Carbon when heated together in a Crucible for at least 20 minutes produces Cu. The Reduction of the Copper with the Carbon produces a copper dust coating which has been displaced in the reduction reaction..

Hope this adds to the repertoire.

Cheers,

Robb.....

Ocean Breeze · Post by **Ocean Breeze** » 23 May 2007, 15:03

Any idea what conc of silver nitrate soln is best for this copper christmas tree? I dont seem to be having much success

Lyn · Post by **Lyn** » 24 May 2007, 01:22

Hi,

You will only need 0.1M silver nitrate solution for this prac. Use clean copper wire about 20cm in length, which has been lightly coiled around a pencil or pen (students can do this as part of their prac).Bend the end of wire so that it hooks over the edge of a normal size test tube. By using a regular test tube you will use far less silver nitrate solution for the reaction. The copper wire is left overnight in the solution for best results. (Have checked out "silver tree" on a variety of websites and the coiled method is referred to as a crazy kind of Christmas tree - near enough. The concentration of silver nitrate solution in the website pracs is also 0.1M.)

P.S. Ask your teachers to provide photocopies of the practicals that they require so that you are not working in the dark. This should provide you with the relevant information that you require to get the pracs organised.

Regards Lyn.

Ocean Breeze · Post by **Ocean Breeze** » 24 May 2007, 08:25

Lyn..
I think that i was using first a 0.003 soln Ag NO3, then trialed a 1 M.(on a very small scale). Neither worked well. So will go right now & make up the 0.1M. Thanks for that.

Ocean Breeze · Post by **Ocean Breeze** » 24 May 2007, 14:15

More help required please!

Re the Hot Cu SO4 & the steel wool(Fe).

Anyone know the equation for the reaction? AND the gas?vapour given off?

Hydrogen? Whats the gas/vapour?

Jazz · Post by **Jazz** » 24 May 2007, 14:36

Fe(s) + CuSO4(aq) = FeSO4(aq) + Cu(s)
when copper(II) sulfate reacts with Iron, Fe metal goes into the solution and the metal(Cu) is formed upon reaction. this is a metal displacement reaction, where the more reactive metal(Fe) displaces the les reactive metal(Cu).

Ocean Breeze · Post by **Ocean Breeze** » 24 May 2007, 15:39

Jazz... so does that mean to keep the equation balaced, theres no gas liberated? We are confused as to whether or not theres a gas given off as well. Is the water involved in any way, and giving off H2 ,O2 etc?

Ocean Breeze · Post by **Ocean Breeze** » 30 May 2007, 14:46

Update on the Christmas tree expt. It went REALLY well. I used tin snips to cut out a Xmas tree shape(from internet)from a sheet of copper. Punched a hole in the top and threaded through fishing line. Suspended in solution using a paddle pop stick. Also coiled a second Xmas tree, made from thick Cu wire, around a cone, and fashioned a trunk on the last twist. This one similarly suspended using fish line. I found a really large rectangular vase, and filled with the 0.1 M/L silver nitrate. The result was amazing. Like a forest snow scene. Every class in the high school had an ooh and ahhh. We took photos every so often to record the process. $\:D/$

SO anyone know if we can smelt/redeem the silver that is now a fluffy sludge at the bottom of the vase?

AND Anyone know a quick way to clean the copper back to shiny? The flat tree I can scrub with steel wool, but not with the coiled Cu wire. How to use reverse electolysis maybe? Which metals to use for the other electrode?

smiley · Post by **smiley** » 06 Jun 2007, 09:45

I have heard about recipes where you add Nitric to the sludgy Silver to recoup it, but my chem teachers here say that you have the problem of the silver not being pure, and not being able to accurately determine what mass of silver you have - given that it's usually wet and sludgy - and therefore you have a solution of indeterminate molarity. So it ends up being not worth it. You can package it up for somebody else to recover it, but from a school point of view just write it off as waste. Sorry to be unhelpful!

Cheers, K

Ocean Breeze · Post by **Ocean Breeze** » 06 Jun 2007, 10:25

Sounds good to me Kristen. One less job for me to do.

Thanks Rainbow Sky

bindi · Post by **bindi** » 07 Jun 2007, 12:02

Hi guys,
I collect the sludge and dry it out and place it into glass jars and label it 'silver' for Y9 Looking at Elements and Metals.
Yes its not perfect but it looks good!

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