Re: Homework Help?

From: Mohammed Farooq (farooq_w_at_hotmail.com)
Date: 09/19/04 

Date: 19 Sep 2004 10:11:05 -0700

Amanda wrote
>hutchy1991@hotmail.com (Hutchy) wrote in message >news:<85bd0f64.0409190241.7d83fc01@posting.google.com>...
> Please can you help with the answers to these equations
>
> Zinc + Copper Suphate = ?
> Magnesium + Copper Sulphate = ?
> Magnesium + Iron Sulphate = ?
> Iron + Copper Sulphate = ?

>Not sulfate like the Americans spell it? BTW, the answer (one of the
>products) for the fourth is already in the reactants of the 3rd one.

>Now, think of the charge (negative charge) of sulfate ions? The
charge
>(positive charge) of Copper ions, i.e. Copper (II) ions (II
represents
>the charge on Coppper ion.)

----------------------------------------------------

>I. The first link obtained from Google Search (using keyword Zinc and
>Copper sulfate reaction) gave me the following:

>( For No. 1 ):
>The spontaneous chemical reaction between zinc metal and aqueous
>copper (II) sulfate [ notice the term copper II ] is conducted so as
>to obtain the available chemical energy released in the form of
>electrical energy.

>The model for this chemical reaction is one where electrons leave the
>zinc:
>Zn + Cu2+ --> Zn2+ + Cu
>(Note: Think the same way about the rest of the equations you are
>asking about.)

>- From the above, you know that 2 electrons leave Zn and react with
>copper II ions. Now you have half the answer. To continue ...
>- Think what Zn2+ (Zinc II ions) would do if there is a sulphate
group
>(with 2 negative charges) around. That 2 negative charges was another
>tip.
>- Your book must have formula for sulphate ion; if not, do google
>search and find it and you are all set.
>- Come up with a chemical formula when combine Zn2+ ion and sulpfate
>ions.

>-------------------------------------------------------------
>Now the answer in chemcial form...

>II. At http://dwb.unl.edu/Chemistry/MicroScale/MScale04.html, look at
>the 2nd equation from the most bottom with the explanation "Zinc
metal
>reacts with copper(II) ions in water to produce copper metal and
>zinc(II) ions. Excess zinc metal dissolves in .....

-------------------------------------------------------------

(For No. 2 )

>III. At the second link of google search (as in I above), under "Word
>Equations - displacement reactions" (I understand that to sort out to
>reach wold be quite a task for you and so..) are

>_______ + copper sulfate ---> magnesium sulfate + _________

>(What "Metal" do you think reacts with copper sulfate to give
>*magnesium* sulphate?)

Amanda,
You have a lot more teaching experience than me (I have had no such
experience), but don't you think the easier approach in teaching such
displacement reactions is by studying the *electrochemical series*
first and then applying that knowledge to predict reaction products,
this apporaoch seems to be more logical. The link you have provided
http://dwb.unl.edu/Chemistry/MicroScale/MScale04.html does show the
reaction between Cu(II) and Zn, but no reason was given as to why Zn
metal dissolves in copper sulfate. Anions like sulfate are usually
spectator ions hence there is no need to consider their chemistry at
this level and just be used for balancing equations.

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