What's New In Chemistry?

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TOPIC: AIR AND ATMOSPHERE

In chemistry, a catalyst is a substance that causes or accelerates a chemical reaction without itself being affected. Catalysts participate in the reactions, but are neither reactants nor products of the reaction they catalyze. In the human body, enzymes are naturally occurring catalysts responsible for many essential biochemical reactions.




In the catalytic converter, there are two different types of catalyst at work, a reduction catalyst and an oxidation catalyst. Both types consist of a ceramic structure coated with a metal catalyst, usually platinum, rhodium and/or palladium. The idea is to create a structure that exposes the maximum surface area of catalyst to the exhaust stream, while also minimizing the amount of catalyst required, as the materials are extremely expensive. Some of the newest converters have even started to use gold mixed with the more traditional catalysts. Gold is cheaper than the other materials and could increase oxidation­, the chemical reaction that reduces pollutants, by up to 40 percent [source: Kanellos].

Most modern cars are equipped with three-way catalytic converters. This refers to the three regulated emissions it helps to reduce.

­The reduction catalyst is the first stage of the catalytic converter. It uses platinum and rhodium to help reduce the NOx emissions. When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2. For example:

2NO => N2 + O2 or 2NO2 => N2 + 2O2
honeycomb catalyst
Ceramic honeycomb catalyst structure.

The oxidation catalyst is the second stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas. For example:

2CO + O2 => 2CO2



There are two main types of structures used in catalytic converters -- honeycomb and ceramic beads. Most cars today use a honeycomb structure.

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TOPIC: ENERGY

A fuel cell that produces power using only water and a warm breeze has been developed by researchers in Germany. The cell could be used to power sensors and military monitoring devices in remote areas.

Most fuel cells rely on the spontaneous formation of water from the combination of hydrogen and oxygen, with the energy produced determined by the changes in enthalpy between the anode and cathode. Storage of hazardous materials such as hydrogen, methanol or hydrides are needed to run these cells. Now, Emil Roduner and Andreas Dreizler at the University of Stuttgart have developed a concentration fuel cell that runs on water and air, making it cheap, safe and easy to refuel.



In Roduner's system, water is oxidized catalytically to molecular oxygen, protons and electrons at the anode, while the reverse reaction takes place at the cathode. As in normal fuel cells, the cathode and anode are separated by a polymer electrolyte membrane which allows the protons to cross to the cathode while the electrons are forced to make their way through a wire, creating a current. The water that forms at the cathode is evaporated by the air flow, keeping the water concentration gradient between the two electrodes, which acts as the driving force for the reaction.

Fuel cell
Electrons created at the anode produce current as they travel through a wire to the anode

Unlike other fuel cells no change in enthalpy occurs as water reacts to form water. This means that typically minor contributions, such as changes in entropy, become key factors in the energy output, explains Roduner. He adds that his inspiration to create the cell came from a desire to demonstrate that 'changes in entropy can still be a driving force [for fuel cells].'

Michael Janik, an expert on fuel cells at the University of Pennsylvania in Philadelphia, US, agrees that this is an unexpected method to develop a fuel cell. Janik comments that typically '[fuel cell chemists] just look at the fuel and the difference in the fuel versus the activation chemistry but Roduner uses concentration as their driving force - that's clever.'

The energy output is smaller than typical fuels cells but this system may find use in specific situations where a small energy output is needed, such as for powering small sensors or for an emergency signal. Roduner envisions its use in dry windy places, such as along the coast or a desert, to facilitate water evaporation at the cathode.

Patricia Pantos


Reference:
"Water and Air Make Energy"
http://www.rsc.org/Publishing/ChemTech/Volume/2010/06/water_air.asp

EXTENDED READING FOR
TOPIC: METALS

Gold has no oxides and is not affected by oxygen in the atmosphere as are other metals. This is why gold does not tarnish -- tarnish is the result of metal reacting with oxygen in a process called oxidation.

Gold is malleable to the point that it can be hammered into a leaf or sheet of foil. Since gold alone is too soft to hold a form, gold is alloyed (combined with other metals) in order to make jewelry.

When gold is alloyed, its ductility is diminished, but its malleability remains constant, except when large percentages of copper are added to the alloy. Nickel used in a white gold alloy has the same characteristics as silver.

Zinc is added to the white gold alloy and lightens the color, but amounts in greater percentage than 14% of the entire alloyed mass will change the color to red and make the alloy brittle. The reason for using zinc in gold alloys is to absorb the oxygen to prevent silver and copper oxides in the mix.

Resource:
"Precious Mineral Marketing Company"
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"Gallery of Unique Wedding Bands & Jewelry"
http://handwovenbands.com/gold.htm