Blog 11.1 Corrosion of Metals [Due Monday 5/23]

1.   a)   Was the penny wrapped in steel wool (made of iron) more or less corroded than

unwrapped penny?

b)     Is this protection from corrosion by using the “coating” technique, or the “sacrificial metal” technique?

c)      The Statue of Liberty was becoming so weak from the corrosion of the copper that it was shut down and “refurbished” in the early 1980’s.  In the process, many iron bands were added to the inside of the statue, making direct contact with the copper.  These bands are now regularly checked and replaced as needed.  Explain why this chemical trickery works to prevent the further oxidation of the copper statue, based on Table J!

My father wrapped the wooden posts on his porch in a product designed to protect the wood.   The product is made out of painted aluminum.  He used iron nails (non-galvanized ones) to nail the aluminum sheets to the wood.  Now after 2 years of weathering, the places where the nails penetrated the aluminum are corroding and crumbling. 

 2.  Explain why this corrosion is happening, in terms of the two metals and Table J.

 

3.  Explain why this problem could have been prevented if the spots where the nails were put in had been sealed with caulking.

3.  Answer the two “Lab Questions” from page 1 of this lab.

Enrichment:

Two metals in contact with each other and moisture will react in what is called a “galvanic reaction.” 

Metal A will be oxidized by the action of oxygen and with the help of the moisture. 

         

                   A (s)  +  O₂  --> The oxide of A^x+  

The Metal B will be oxidized as well, but this happens as it tries to restore electrons to the first metal.

                  

                   B (s)  +  A^x+  --> A  +  B^y+

This process can be helpful (as in the case of a ship hull being protected) or destructive…

Based on the description of my father’s corrosion problem in the Conclusion section, decide with Metal is “A” and which is “B.”  Write the reactions shown above, using actual metals in place of A, A^x+, B and B^y+.  Make sure you pay attention to proper ion charges (Fe becomes Fe²⁺).

Blog 11.2 Table J and Metal Reactivity (Due Monday 5/16)

Blog Questions:

1.      The solutions you used were all nitrate solutions. For example, the silver ion solution (Ag¹⁺) is really a solution of silver nitrate (AgNO₃). The complete REDOX equation for the reaction between magnesium metal and silver solution is as follows:

         

              Mg_(s)    +    AgNO_3(aq)     -->    Mg(NO₃)_2(aq)   +    Ag_(s)

a) The nitrate ion is known as a “spectator ion”.  Explain why you think this name is appropriate:

b) In the reaction between magnesium and silver solution, what is oxidized

What is reduced?  

2. Propose a rule that predicts whether or not metal X and metal ion Y⁺² will react, based on Table J.

3.  Answer the two “lab questions” from page 1 of this lab:

1.    What is an “ACTIVity series” and how does it relate to what I already know about the behavior of metallic and non-metallic elements?

2.   How is an activity series used to predict (or explain) which metal (or non-metal) is more reACTIVE than another?

4. History of Metals

Currently there are 86 known metals. Before the 19th century only 24 of these metals had been discovered and, of these 24 metals, 12 were discovered in the 18th century. Therefore, from the discovery of the first metals, gold and copper, until the end of the 17th century, some 7700 years, and only 12 metals were known. Four of these metals, arsenic, antimony, zinc and bismuth, were discovered in the thirteenth and fourteenth centuries, while platinum was discovered in the 16th century. The other seven metals, known as the “Metals of Antiquity,” were the metals upon which civilization was based. The first 4 had been discovered and were in use before cultures had developed the ability to communicate in writing.  They are referred to in the oldest written documents we can find (like the book of Genesis in the Bible, as well as ancient Egyptian, Phoenician and Babylonian texts).  These seven metals were:

1.     Gold, 6,000 BC

2.     Copper, 4,200 BC

3.     Silver, 4,000 BC

4.     Lead, 3,500 BC

5.     Tin, 1,750 BC

6.     Iron, 1,500 BC

7.     Mercury, 750 BC

On Table J, the elements above H₂ are prone to oxidation in the air, and are therefore unlikely to be found in pure form on the Earth’s surface.  Rather, they are in compounds called “ores” which are metal oxides, like Fe₂O₃ (iron ore).  Why do you think gold, silver and copper were discovered so long ago by humans, but the other 4 metals were discovered later?

 

5.  https://www.e-education.psu.edu/files/matse081/animations/lesson04/u04_metalWork.html

A significant advance in human civilization occurred when humans discovered how to extract copper from copper ore.  When mixed with tin, the alloy is called bronze and is harder than either metal separately.  Go to this website.  Check out two things:

·         How copper was “smelted” in ancient times.

·         How bronze was made.

 

Enrichment:

Ag¹⁺ is a very important ion in the history of Rochester, since it was the primary ingredient in George Eastman’s black and white KODAK film industry.  Research how this ion is used in photography.