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Topic: Activity and solubility of metals  (Read 9458 times)

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Offline Juozukas

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Activity and solubility of metals
« on: January 04, 2008, 10:40:44 AM »
Hi,
1. Problem:
A solution of copper sulphate is poured into two test tubes and 2 drops of dilute (1:2) sulphuric acid are added to each of them. Magnesium powder is added to the solution in one test tube and a piece of iron is placed in the solution in the second test tube. Dark brown copper is formed and the blue color of the solutions disappears.
I made this experiment during my chemistry laboratory works, but i don't understand how to write the ionic equation, can anyone help me? :)

i believe that molecular eq should look like this:
CuSO4+Mg  H2SO4>  MgSO4+Cu

Is it right? or I'm desperate at chemistry? :P

2. question: electronic equation is the same thing as redox equation? if not, than please give me some examples about electronic equations.
3. which metals dissolve in phosphoric acid? why there are so few of them? (can't find anything about this in the book or in google)

Offline LQ43

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Re: Activity and solubility of metals
« Reply #1 on: January 04, 2008, 04:13:42 PM »
i believe that molecular eq should look like this:
CuSO4+Mg  H2SO4>  MgSO4+Cu

Is it right? or I'm desperate at chemistry? :P

1. This equation is correct. (there is also another reaction going on - what is the purpose of the H2SO4)

for the ionic equation, rewrite the equation but use the ions of CuSO4 and MgSO4 in their places

2. not sure what the electronic equation is unless they mean the half reactions showing the numbers of electrons lost and gained


Offline Juozukas

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Re: Activity and solubility of metals
« Reply #2 on: January 05, 2008, 06:57:46 AM »
i believe that molecular eq should look like this:
CuSO4+Mg  H2SO4>  MgSO4+Cu

Is it right? or I'm desperate at chemistry? :P

1. This equation is correct. (there is also another reaction going on - what is the purpose of the H2SO4)

for the ionic equation, rewrite the equation but use the ions of CuSO4 and MgSO4 in their places

2. not sure what the electronic equation is unless they mean the half reactions showing the numbers of electrons lost and gained


i don't get it.. you mean there should be 2 molecular equations? and about the ionic equation, if i understood correctly, than the molecular and ionic equations will be the same... or I'm wrong?
« Last Edit: January 05, 2008, 01:27:49 PM by Juozukas »

Offline Kryolith

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Re: Activity and solubility of metals
« Reply #3 on: January 05, 2008, 03:46:05 PM »
oxidation: Mg ----> Mg2+ + 2 e-
reduction: Cu2+ + 2 e- ----> Cu
redox: Mg + Cu2+ ----> Mg2+ + Cu

The reaction takes place, because Cu/Cu2+ has a higher redox potential than Mg/Mg2+.

I don't know, how you call the equations.

Offline LQ43

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Re: Activity and solubility of metals
« Reply #4 on: January 05, 2008, 05:59:02 PM »
Quote
Quote
for the ionic equation, rewrite the equation but use the ions of CuSO4 and MgSO4 in their places


i don't get it.. you mean there should be 2 molecular equations? and about the ionic equation, if i understood correctly, than the molecular and ionic equations will be the same... or I'm wrong?


The ions of CuSO4 are Cu+2 and SO42-

what would the ions of MgSO4 be?

molecular equation:

CuSO4 + Mg --> Cu +  MgSO4

ionic equation:

Cu+2 + SO42-  +  Mg  -->  Cu + (ions of MgSO4)

Kryolith is giving you the half reaction equations - probably what the question means by electronic equations

3. (others may want to add or correct the following):

when acids react with metals there are 2 ways they can do this:
- using H+
most/all acids can oxidized metals this way but strong acids do it faster and more efficiently than weak acids

what kind of acid is phosphoric acid?


- using the anion part
only acids that have a strong oxidizing anion like HNO3 can oxidize metals with their anions, these are called oxidizing acids

acids whose anions are poor oxidizers like HCl are called non-oxidizing acids

what kind of acid is phosphoric acid?


An acid that is a strong acid and has a strong oxidizing anion will react readily with many metals.

What can you conclude about phosphoric acid and its ability to react with metals based on the these two properties?
 
« Last Edit: January 05, 2008, 07:31:09 PM by LQ43 »

Offline Juozukas

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Re: Activity and solubility of metals
« Reply #5 on: January 06, 2008, 11:11:49 AM »
Quote
Quote
for the ionic equation, rewrite the equation but use the ions of CuSO4 and MgSO4 in their places


i don't get it.. you mean there should be 2 molecular equations? and about the ionic equation, if i understood correctly, than the molecular and ionic equations will be the same... or I'm wrong?


The ions of CuSO4 are Cu+2 and SO42-

what would the ions of MgSO4 be?

molecular equation:

CuSO4 + Mg --> Cu +  MgSO4

ionic equation:

Cu+2 + SO42-  +  Mg  -->  Cu + (ions of MgSO4)

Kryolith is giving you the half reaction equations - probably what the question means by electronic equations

3. (others may want to add or correct the following):

when acids react with metals there are 2 ways they can do this:
- using H+
most/all acids can oxidized metals this way but strong acids do it faster and more efficiently than weak acids

what kind of acid is phosphoric acid?


- using the anion part
only acids that have a strong oxidizing anion like HNO3 can oxidize metals with their anions, these are called oxidizing acids

acids whose anions are poor oxidizers like HCl are called non-oxidizing acids

what kind of acid is phosphoric acid?


An acid that is a strong acid and has a strong oxidizing anion will react readily with many metals.

What can you conclude about phosphoric acid and its ability to react with metals based on the these two properties?
 




so the phosphoric acid is weak acid, so it can react only with these metals: Li, K, Ba, Sr, Ca, Na, Mg, Be, Al(high activity metals), or not?

Offline LQ43

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Re: Activity and solubility of metals
« Reply #6 on: January 06, 2008, 07:25:05 PM »
I think you can go up to Fe,

 Liquid phosphoric acid reacts with active metals (e. g. aluminum, zinc, iron, from http://www.jtbaker.com/msds/englishhtml/p3984.htm


 

Offline jray

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Re: Activity and solubility of metals
« Reply #7 on: January 08, 2008, 07:26:37 AM »
Can tin dissolve in concentrated sulphuric acid? If it does, then Sn with +2 or +4 oxidation number?
Sn + H2SO4 -concentrated-> SnSO4 + H2O + SO2 ?

Offline AWK

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AWK

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