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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: firedamage on February 07, 2009, 07:59:20 PM

Title: help\
Post by: firedamage on February 07, 2009, 07:59:20 PM
in one of the experiment:
1)transfer 1 M CuSO4 solution into each of the 2 test tubes to a depth of 2 cm.Obtain a small piece of zinc metal.
2)Add the zinc metal to the CuSO4 solution in one of the test tube.the CuSO4 solution in the other test tube is your reference for the initial solution the test tube in your test tube rack and observe and record the colour of the CuSO4 solution and zinc metal again after 15 and 30 minutes.

Here i get the result:After 15 min(Zinc metal become brown colour,Bubbles were realeased within the solution)

                            After 30 min(Zinc metal become reddish-brown colour.there
                              were percipitate formed in the bottom of the test tube)

Can anyone tell me why zinc metal become brwn clour after 15 min?why it form percipitate after 30 min?Why the solution become hot?
Title: Re: help\
Post by: ARGOS++ on February 07, 2009, 08:27:13 PM
Dear firedamage;
Can you answer your own question with the help of:


And please name your topic not only with help, give it next time a more descriptive name
Good Luck!
Title: Re: help\
Post by: Arkcon on February 07, 2009, 08:45:06 PM
Also, can you break down your step by step description into a chemical equation?  You can probably guess, the test tube, the cm length, the test tube rack don't really enter into the question, right?
Title: Re: help\
Post by: firedamage on February 08, 2009, 04:04:23 AM
the chemical equation is Zn+CuSO4=Cu+ZnSO4..
the percipitate formed is copper?
why there is bubbles released?is it chemical reaction has occur?
Title: Re: help\
Post by: Arkcon on February 08, 2009, 07:44:15 AM
Correct.  It is a little funny, the color and texture of the precipitate, this is just one of those things you have to learn by experience.  Finely divided metal may not be shiny.  For example, finely divided (precipitated) platinum, or nickel are often black.  So look at it this way, you're now ahead of the other chemistry noobs.  I hope, when you answer their questions on this forum, you're as subtle as we are.

As to the bubbles, I'm not really sure.  I'm sure I saw them, back in the day, but couldn't figure them out either.  Transition metal salts, in solution, do function as Lewis acids, with  water, leaving more H+ free, so maybe that was hydrogen, from an acid reaction?  Again, it's something you now know, that you didn't before.