Electrochem

[Ninjakat]

How do u create an activity series?

 

Bah... I honestly dont get this. Its electro chem

 

Question: Consider the following lab data, gathered from two different students

 

Student 1: Lab data for the determination of an activity series of metals

 

Chemical | Ag+(aq) | Ni+2 (aq) | Pb+2(aq) | Zn+2 (aq)

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

Ag(s) |//////////////| No change | No change | No change

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

Ni(s) | Grey coating| /////////////| Black coating| No change

forms on nickle forms on nickle

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

Pb(s) | Grey coating| No change |//////////////| No change

forms of lead

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

Zn(s) |Grey coating | grey coating | Black coating |///////////

in forms of zinc|in forms of zinc| in forms of zinc

 

 

Student 2: Lab data for the determination of an activity series of metals

 

Chemical | Ag+(aq) | Ni+2 (aq) | Pb+2(aq) | Zn+2 (aq)

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

Ag(s) |//////////////| Grey coating on silver | black coating on silver | grey coating on silver

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

Ni(s) | Grey coating| /////////////////////////| No change | No change

forms on nickle

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

Pb(s) | Grey coating| Grey on coating lead |////////////////////////////| No change

forms of lead

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

Zn(s) |No change | No change | No change | //////////////

 

 

 

a) Which student has valid results? (Hint: use the data to create an activity series.) Justify your answer by stating the errors in the incorrect observation table.

 

B) Suggest two reasons why a student may experience poor results during this type of chemical experiment.

[cypress]

You can create an activity series from this data by understanding what a metal activity series is. Did you know that in electro chemistry element to ion oxidation reduction reactions follow an order from most active lithium to least active gold? This means that the lesser active metal ion will oxidize a more active elemental metal. From this, and the data, you should be able to construct an activity series from each of the two result sets. If one of the two activity series is internally inconsistent then that data set must be wrong. If they are both internally consistent but one does not match the activity series posted online or in your chemistry text then the one that does not match is wrong.

[mississippichem]

I'll second Cypress' advice.

 

You also might try wikipedia for a good activity series. It might also be listed under "electrochemical series". Be careful on the sign convention though if you're reading a chart. Most data uses postitive potential values for oxidizers. but beware! Some data from various parts of the world uses the reverse sign convention. These you have listed are all metals though, it shouldn't cause a problem.

Edited December 1, 2010 by mississippichem

[Ninjakat]

Thank you I was able to find the activity series but what doesnt make sense is both of them dont really work 100%

 

With silver mixing with nickle because its closer together on the activty series, one chart states (no change) although the other one does.

There should be a reaction, ALTHOUGH it also states on the second chart silver reacts slightly with zinc, but they are polar opposites on the activity series... doesnt that mean they arent supposed to react?

[mississippichem]

Thank you I was able to find the activity series but what doesnt make sense is both of them dont really work 100%

 

With silver mixing with nickle because its closer together on the activty series, one chart states (no change) although the other one does.

There should be a reaction, ALTHOUGH it also states on the second chart silver reacts slightly with zinc, but they are polar opposites on the activity series... doesnt that mean they arent supposed to react?

 

The metals near the lithium side of the series are more likely to give up electrons: they are more likely to be oxidized, so they are the strong reducing agents. The metals near the gold side of the series are less likely to give up electrons: they are less likely to be oxidized, so they are weak reducing agents. The series actually continues past gold but it gets to metalloids and non-metals which are the stronger oxidizing agents and have a tendency to be reduced.

 

So one could say for example that lithium, being a strong reducing agent is a very poor oxidizing agent. One could also say that gold is a stronger oxidizing agent than lithium because gold is from the weak reducing agent side of the series. The further apart two metals are on the activity series, the more electrochemically favored the reaction is between them. So in that sense metals on the table that are far apart from each other are likely to show a reaction. The opposite is true of metals close to each other on the activity series. There are many other factors to consider in reality, but this should suffice for your assignment.