Chemical Behavior of Metals Chapter 3: Activity 3

Solutions Solid copper chloride is added to water CuCl2(s) → Cu+2(aq) + 2Cl-1(aq)

Which Metals Won’t Corrode? What would happen if solid metal ZINC was placed in a copper chloride solution? Zn (s) + Cu(Cl)2 (aq) ?

Single Replacement Reaction When solid ZINC was placed in a copper chloride aqueous solution….. Zn (s) + Cu(Cl)2 (aq) ZnCl2 (aq)+ Cu (s)

Single Replacement Reaction When 1 reactant replaces another reactant of the same type. -Metals will replace Metals -Nonmetals will replace Nonmetals

Online animation

Single Replacement Reaction Why do Metals Replace Each Other? Some metals want to lose electrons. Some metals want to gain electrons.

Use the Activity Series of Metals to determine if a reaction will occur

Is Zn higher than Cu on the list? Use the Activity Series of Metals to determine if a reaction will occur Is Zn higher than Cu on the list? Li K Ba Sr Ca Na Mg Al Mn Zn Fe Cd Co Ni Sn Pb H Cu Ag Hg Au

Activity Series of Metals Li K Ba Sr Ca Na Mg Al Mn Zn Zn + CuCl2 → ZnCl2 + Cu Fe Cd Co Ni Sn Pb H Cu Ag Hg Au YES Zn is Higher than Cu Decreasing Activity

So what is happening? Zn is more reactive than Cu It will lose it’s outer most electrons (valence electrons) easier than Cu will and will become a Zn+2.

Cl-1 Cl-1 Cu+2 Notice the copper is an ion and floating around freely Cl

So what is happening? . Zinc is an atom, loses it’s electrons to copper and then zinc becomes an ion

Cl-1 Zn+2 Cl-1 Cl-1 Cl-1 After the reaction, zinc is now in solution Cl

Recap In solution, metals are floating around by themselves as ions Metals that are higher on the Activity Series are more reactive than metals lower on the list Metals that are higher are more reactive and want to lose their valence electrons

Yesterday’s Activity Solid aluminum was added to a solution of copper chloride Al(s) + CuCl2(aq) → Cu(s) + AlCl3(aq) So, solid aluminum went into solution and copper came out of solution!!!! WHY???????

Some practice Will this reaction happen? Cu + AgNO3→ ? Yes, Cu is higher on the list Cu + AgNO3→ Ag + Cu(NO3)2 So, after the reaction, silver is now the solid!

Some practice Will this reaction happen? Cu + Pb(NO3)2→ ? No, Cu is lower on the list Cu + Pb(NO3)2 → No Reaction So, copper is still a solid

A device that converts chemical energy to electrical energy. Batteries A device that converts chemical energy to electrical energy. Metals that are farther apart on the activity series will produce a more efficient battery

Batteries Li K Ba Sr Ca Na Mg Al Mn Zn Fe Cd Co Ni Sn Pb H Cu Ag Hg Au 0.51

How Batteries Work Video

Car Battery Battery Reactions and Chemistry © Photographer: Anthony Berenyi | Agency: Dreamstime.com A car has a lead-acid battery, which has a reversible reaction. In any battery, an electrochemical reaction occurs like the ones described on the previous page. This reaction moves electrons from one pole to the other. The actual metals and electrolytes used control the voltage of the battery -- each different reaction has a characteristic voltage. For example, here's what happens in one cell of a car's lead-acid battery: The cell has one plate made of lead and another plate made of lead dioxide, with a strong sulfuric acid electrolyte in which the plates are immersed. Lead combines with SO4 (sulfate) to create PbSO4 (lead sulfate), plus one electron. Lead dioxide, hydrogen ions and SO4 ions, plus electrons from the lead plate, create PbSO4 and water on the lead dioxide plate. As the battery discharges, both plates build up PbSO4 and water builds up in the acid. The characteristic voltage is about 2 volts per cell, so by combining six cells you get a 12-volt battery. A lead-acid battery has a nice feature -- the reaction is completely reversible. If you apply current to the battery at the right voltage, lead and lead dioxide form again on the plates so you can reuse the battery over and over. In a zinc-carbon battery, there is no easy way to reverse the reaction because there is no easy way to get hydrogen gas back into the electrolyte. Modern Battery Chemistry Modern batteries use a variety of chemicals to power their reactions. Typical battery chemistries include: Zinc-carbon battery - Also known as a standard carbon battery, zinc-carbon chemistry is used in all inexpensive AA, C and D dry-cell batteries. The electrodes are zinc and carbon, with an acidic paste between them that serves as the electrolyte. Alkaline battery - Alkaline chemistry is used in common Duracell and Energizer batteries, the electrodes are zinc and manganese-oxide, with an alkaline electrolyte. Lithium-iodide battery - Lithium-iodide chemistry is used in pacemakers and hearing aides because of their long life. Lead-acid battery - Lead-acid chemistry is used in automobiles, the electrodes are made of lead and lead-oxide with a strong acidic electrolyte (rechargeable). Nickel-cadmium battery - The electrodes are nickel-hydroxide and cadmium, with potassium-hydroxide as the electrolyte (rechargeable). Nickel-metal hydride battery - This battery is rapidly replacing nickel-cadmium because it does not suffer from the memory effect that nickel-cadmiums do (rechargeable). Lithium-ion battery - With a very good power-to-weight ratio, this is often found in high-end laptop computers and cell phones (rechargeable). Zinc-air battery - This battery is lightweight and rechargeable. Zinc-mercury oxide battery - This is often used in hearing-aids. Silver-zinc battery - This is used in aeronautical applications because the power-to-weight ratio is good. As you can see, several of these batteries are rechargeable. What makes a battery rechargeable? In the next section, we'll check out how rechargeable batteries work.

Why do metals react? Metals that are more reactive want to LOSE electrons This is called OXIDATION Cu + AgNO3→ Ag + Cu(NO3)2 When the less reactive metal GAIN these lost electrons This is called REDUCTION SO… Cu Lost Electrons = Oxidation Ag Gained Electrons = Reduction 0 +1 0 +2

REDOX REACTIONS LEO the lion goes GER Losing Electrons is Oxidation Gaining Electrons is Reduction

OXIDATION Oxidation Mg + S MgS Mg lost electrons Mg has been oxidized +2 Mg has been oxidized OXIDATION

REDUCTION Reduction Mg + S MgS S gained electrons -2 Sulfur has been reduced REDUCTION

Leo the lion goes Ger Mg + S MgS S is REDUCED -2 +2 Mg is Oxidized

Applications of Metal corrosion reactions What is this??? 32

Applications of Metal corrosion reactions MRE Because of the importance of a hot meal, all military MREs come packaged with a flameless heater. The flameless heater uses a simple chemical reaction to provide sufficient heat to warm the food. Photo courtesy U.S. Department of Defense A Marine demonstrates a flameless heater. Chemical heating is actually a pretty widespread natural phenomenon. Everyone has seen iron rust. Rust is a natural process in which iron atoms combine with oxygen atoms to create reddish, crumbly iron oxide. The process is normally very slow, but we all know that wet iron rusts faster. Iron exposed to salty ocean water rusts the fastest. When iron turns to rust, the oxidation process generates heat. But rust forms so slowly that the heat generated is unnoticeable. We are all familiar with much faster oxidation reactions as well. For example, when you "oxidize" the carbon atoms in a charcoal briquette, they get quite hot. We use the word burning to describe this high-speed sort of oxidation. The idea behind a flameless heater is to use the oxidation of a metal to generate heat. Magnesium metal works better than iron because it rusts much more quickly. To make a flameless heater, magnesium dust is mixed with salt and a little iron dust in a thin, flexible pad about the size of a playing card. To activate the heater, a soldier adds a little water. Within seconds the flameless heater reaches the boiling point and is bubbling and steaming. To heat the meal, the soldier simply inserts the heater and the MRE pouch back in the box that the pouch came in. Ten minutes later, dinner is served! 33

The idea behind a flameless heater is to use the oxidation of a metal to generate heat. Magnesium metal works better than iron because it rusts much more quickly. To make a flameless heater, magnesium dust is mixed with salt and a little iron dust in a thin, flexible pad about the size of a playing card. To activate the heater, a soldier adds a little water. Within seconds the flameless heater reaches the boiling point and is bubbling and steaming. To heat the meal, the soldier simply inserts the heater and the MRE pouch back in the box that the pouch came in. Ten minutes later, dinner is served!

MRE

Daniels Electrochemical Cell Video