H2S Helps Hearts

NO and H₂S are two important gases that regulate heart function in humans.

H₂S is a colourless, poisonous, flammable gas with the characteristic foul odour of rotten eggs at concentrations up to 100 parts per million. It is produced in swamps and sewers from the bacterial breakdown of organic matter in the absence of oxygen. It also occurs in volcanic gases, natural gas, and is produced naturally in the human body as a signalling molecule.

NO which also occurs naturally in the body, is highly reactive, having a biological lifetime of a few seconds, yet diffuses freely across membranes. People who live at high altitudes have higher levels of NO which helps them live with the lower oxygen concentration.

Scientists at the Peninsula Medical School at the University of Exeter and the National University of Singapore have analyzed the complex 'cross talk' between H₂S and NO and found that the interaction may offer potential strategies in the management of heart failure. The two gases were found to interact together to form a thiol-sensitive compound (probably HNO) which produces muscular contraction and muscular relaxation effects in the heart. This crosstalk suggests that there is the potential to produce a molecule that may be of benefit to the heart and which could be the basis of a new drug therapy based on elements that occur naturally in the body.

Reference
Qian-Chen Yong, Jia Ling Cheong, Fei Hua, Lih-Wen Deng, Yok Moi Khoo, How-Sung Lee, Alexis Perry, Mark Wood, Matthew Whiteman, Jin-Song Bian. Regulation of Heart Function by Endogenous Gaseous Mediators—Crosstalk Between Nitric Oxide and Hydrogen Sulfide. Antioxidants & Redox Signaling, 2011; 14 (11): 2081 DOI: 10.1089/ars.2010.3572

Further Reading
Naming Ionic Compounds
Molecular Mass (Formula Weight)
Percentage Composition
Concentration (ppm)
Lewis Structures
Shapes of Molecules
Molecule Polarity
Intermolecular Forces

Study Questions:

1. Name each of the following compounds:
   
   • H₂S
   • NO
   • HNO
2. Calculate the molecular mass (formula weight) for each of the following:
   
   • H₂S
   • NO
   • HNO
3. Calculate the percentage composition of each of the following:
   • H₂S
   • NO
   • HNO
4. H₂S can be detected by its odour at concentrations of 100ppm. Convert this to a concentration in
   
   • mg/L
   • μg/mL
   • % by mass (% by weight)
   • mol/L (M)
5. Draw a Lewis Structure (electron dot diagram) for each of the following molecules
   
   • H₂S
   • NO
   • HNO
6. Describe the shape of each of the following molecules:
   • H₂S
   • NO
   • HNO
7. Label each of the following molecules as polar or non-polar and explain why:
   • H₂S
   • NO
   • HNO
8. Which of the following molecules is most likely to have the highest boiling point, and explain why:
   • H₂S
   • NO
   • HNO
   
   
   
   

Multiferroic Alloy

University of Minnesota scientists have discovered a new alloy that converts heat directly into electricity. In theory, an alloy like this could be used to capture waste heat from a car's exhaust and use it to produce electricity to charge the car's battery. Similarly, a thin film of this alloy could be used to convert waste heat from computers into electricity.
The alloy is made out of nickel, cobalt, manganese and tin and has the formula Ni₄₅Co₅Mn₄₀Sn₁₀.
This new alloy undergoes a highly reversible phase transformation in which one solid turns into another solid with very different magnetic properties. This means that the new alloy begins as a non-magnetic material, then suddenly becomes strongly magnetic when the temperature is raised a small amount. When this happens, the material absorbs heat and spontaneously produces electricity in a surrounding coil.
Substances which combine unusual magnetic and electric properties such as this alloy are called multiferroic materials. Other multiferroic materials include TbMnO₃, HoMn₂O₅, LuFe₂O₄, BiFeO₃ and BiMnO₃.

In the demonstration below, "University of Minnesota researchers show how a new multiferroic material they created begins as a non-magnetic material then suddenly becomes strongly magnetic as the piece of copper below is heated a small amount. When this happens, it jumps over to a permanent magnet. This demonstration represents the direct conversion of heat to kinetic energy."




Reference
Vijay Srivastava, Yintao Song, Kanwal Bhatti, R. D. James. The Direct Conversion of Heat to Electricity Using Multiferroic Alloys. Advanced Energy Materials, 2011; 1 (1): 97 DOI: 10.1002/aenm.201000048

Further Reading
Metals and Non-metals
Physical and Chemical Changes
Pure Substances and Mixtures
Percentage Composition

Study Questions

1. What is meant by the term "alloy"?
2. What is meant by the term "multiferroic material"?
   
3. Calculate the percentage composition of the following multiferroic materials:
   
   • TbMnO₃
   • HoMn₂O₅
   • LuFe₂O₄
   • BiFeO₃
   • BiMnO₃
   • Ni₄₅Co₅Mn₄₀Sn₁₀
4. Which of the above substances would be classified as alloy(s)? Explain your answer.
5. Which of the substances in question 3 would be classified as mixture(s)? Explain your answer.
   
6. What similarities can you see in the multiferroic materials listed in question 3?
   
7. How do you think these similarities contribute to their magnetic and electrical properties?
   

Restricting Chemical Sales

Police in Western Australia want to restrict stores selling some chemicals in a bid to "smash" clandestine drug laboratories according to a story in the Courier Mail today.
The list of chemicals being targeted includes drain cleaners, battery acid, and common lawn fertilizers.

Drain cleaners often contain sodium hydroxide, also known as caustic soda or lye. Sodium hydroxide, a white solid at room temperature, is a strong base that can cause chemical burns.
When sodium hydroxide is added to a blocked drain it dissolves in the water in the pipe and releases heat. This heat can melt the grease blocking the pipe. The sodium hydroxide also reacts with some of the fat in the pipe to form soap. This soap helps remove the grease blocking the drain.

Lead-acid batteries that are typically found in cars contain sulfuric acid, also known as vitriol. It is a strong acid that used in concentrations of around 30% w/w in battery acid. When sulfuric acid dissolves in water, heat is given off. Sulfuric acid can be neutralized by sodium hydroxide with the products of the reaction being water and sodium sulfate.

High-nitrogen content fertilizers can contain ammonium nitrate which is itself a white solid at room temperature and pressure. When ammonium nitrate dissolves in water it absorbs energy from the surroundings. Ammonium nitrate reacts with sodium hydroxide to produce ammonia gas, water and sodium nitrate.
Ammonia is a colourless gas with a pungent odour at room temperature and pressure. "Household ammonia", sold as a cleaning product for ovens, glass, porcelain and stainless steel, is a solution of ammonia in water. The concentration of this basic solution varies from 5% w/w to 10% w/w.
Ammonia is used to make many pharmaceuticals.

Reference
http://www.couriermail.com.au/news/national/police-bid-to-restrict-chemical-sales/story-e6freooo-1226077611068

Further Reading
Naming Ionic Compounds
Writing Ionic Formula
Definitions and Properties of Acids and Bases
Enthalpy Change
Concentration: Percent by Mass
Concentration: Molarity


Study Questions

1. Give the chemical formula for the following compounds:
   
   • sodium hydroxide
   • sulfuric acid
   • sodium sulfate
   • ammonia
   • ammonium nitrate
   • sodium nitrate
   • water
2. Draw up a table with the headings, acidic, basic, neutral. Place the compounds listed above in the appropriate places in the table.
3. Draw up a table with the headings ionic and covalent. Place the compounds listed in question 1 in the appropriate places in the table.
4. Define the terms exothermic and endothermic.
5. Write an equation to show sodium hydroxide dissolving in water. Include the energy term. Is this reaction exothermic or endothermic?
6. Write an equation to show sulfuric acid dissolving in water. Include the energy term. Is this reaction endothermic or exothermic?
7. Write an equation to show ammonium nitrate dissolving in water. Include the energy term. Is this reaction endothermic or exothermic?
8. Convert the following percent by mass concentrations to concentrations in mol/L
   
   • 30% w/w aqueous sulfuric acid solution
     
   • 5% w/w aqueous ammonia solution
   • 10% w/w aqueous ammonia solution
9. Write balanced chemical equations for each of the following:
   
   • the neutralization of sulfuric acid by sodium hydroxide in aqueous solution
   • ammonium nitrate reacts with sodium hydroxide in solution
10. Write an equation to show how sodium hydroxide can react with a fat to produce soap.
11. Explain how soap can clean up built up grease in your drain.
12. A student found a container of solution in the family's garage. it is believed to be either household cleaner or battery acid. Describe tests that you could conduct in order to determine what solution is in the container. What safety precautions would you take when conducting these tests?
    

Metallic Hydrogen Superconductor

Superconductors are materials that permit electricity to travel freely, without resistance, so they could dramatically improve the efficiency of power transmission technologies. Metallic hydrogen should be just such a superconductor.

Liquid metallic hydrogen is thought to exist in the high-gravity interiors of Jupiter and Saturn.
Scientists have predicted that electricity would flow, uninhibited, through a material made by compressing hydrogen into a metal. But so far, on Earth, researchers have been unable to use such compression techniques to squeeze hydrogen under high enough pressures to convert it into a metal. University at Buffalo chemists have now proposed an alternative solution for metallizing hydrogen by adding sodium to hydrogen which they think might make it possible to convert the compound into a superconducting metal under significantly lower pressures.

NaH₉, which does not occur naturally on Earth but is expected to be a stable compound, is predicted to become metallic at an experimentally achievable pressure of about 250 gigapascals, about 2.5 million times Earth's standard atmospheric pressure, but less than the pressure at Earth's core which is about 3.5 million atmospheres.

Reference
University at Buffalo (2011, June 13). Under pressure, sodium, hydrogen could undergo a metamorphosis, emerging as superconductor. ScienceDaily. Retrieved June 15, 2011, from http://www.sciencedaily.com­ /releases/2011/06/110613162240.htm

Further Reading
Metals and Non-metals
Kinetic Theory of Gases

Study Questions

1. Draw up a table listing the properties of metals and non-metals.
2. In what ways is elemental hydrogen like a non-metal?
3. In what ways is elemental hydrogen like a metal?
4. Use the Kinetic Theory of Gases to explain what you expect to happen as elemental hydrogen at atmospheric pressure is subjected to increasing pressure.
5. Using the Kinetic Theory of Gases, describe two ways that scientists could, in theory, make solid hydrogen.
6. Using the Kinetic Theory of Gases, explain why hydrogen might exist as a liquid in the interior of the planet Jupiter.
   
7. If 250 gigapascals is about 2.5 million times Earth's standard atmospheric pressure, what does the prefix "giga" stand for?
   
8. Why do you think that chemists suggest adding sodium to hydrogen to create a solid material capable of conducting electricity?
   

Nickel Isotopes

Atoms of an element with the same number of protons but a different number of neutrons are known as isotopes. Nickel, atomic number (Z) = 28, has 28 protons in its nucleus. There are at least 30 isotopes of nickel, including the stable isotopes nickel-58, nickel-60, nickel-61, nickel-62 and nickel-64, and the radioactive isotopes nickel-56 and nickel-59.
Nickel-56 is produced in some supernovae in which nickel-56 then decays to cobalt-56 and then to iron-56. The half-life of nickel-56 is about 6 days.
Nickel-59 has been used to date the age of meteorites because it has a long half-life of 76,000 years.

Scientists from the Nuclear Spectroscopy Division at the Institute of Experimental Physics (IFD) of the Faculty of Physics, University of Warsaw (FUW) have undertaken research into nickel-48, a highly peculiar isotope which was only discovered in 1999. It has 28 protons and only 20 neutrons in its nucleus.

Nickel-48 is the most neutron deficient nucleus ever studied. Such an isotope "lives" only 2 thousandths of a second and then decays. The research by the Polish scientists from FUW has shown that the most frequent decay mode of nickel-48 is two-proton emission in which 2 protons are emitted from the nucleus. This simultaneous two-proton emission is a very rare phenomenon. So far it has only been observed in three other atomic nuclei: magnesium-19, zinc-54 and iron-45.

Reference
University of Faculty of Physics Warsaw (2011, June 9). Unique Polish detector can observe rare decays of nickel nuclei. ScienceDaily. Retrieved June 10, 2011, from http://www.sciencedaily.com­ /releases/2011/06/110609084811.htm

Further Reading
Isotopes
Nuclear Decay
Half-Life

Study Questions

1. What is the mass number of each of the following isotopes?
   
   • nickel-58
   • nickel-62
   • magnesium-19
   • zinc-54
   • iron-45
2. What is the atomic number of each of the following isotopes ?
   
   • nickel-58
   • nickel-62
   • magnesium-19
   • zinc-54
   • iron-45
3. How many protons are present in an atom of each of the following isotopes?
   
   • nickel-58
   • nickel-62
   • magnesium-19
   • zinc-54
   • iron-45
4. How many neutrons are present in an atom of each of the following isotopes?
   
   • nickel-58
   • nickel-62
   • magnesium-19
   • zinc-54
   • iron-45
5. Write nuclear decay equations for each of the following:
   
   • nickel-56 decays to cobalt-56
   • cobalt-56 decays to iron-56
   • nickel-48 decays by emitting 2 protons from the nucleus
   • magnesium-19 decays by emitting 2 protons from the nucleus
6. Using a half-life of 76,000 years for nickel-59, calculate how much nickel-59 will remain in a 50g pure sample in:
   • 38,000 years
   • 152,000 years
7. If a meteorite is approximately 1.2 million years old, what percentage of the original nickel-59 would remain?
8. If a meteorite has a mass of 600kg and contains 10% nickel-59, what mass of nickel-59 will remain in 380,000 years?
   

Sodium ion Batteries

To connect solar and wind energy sources to the electrical grid, grid managers require batteries that can store large amounts of energy created at the source. Lithium ion rechargeable batteries, common in consumer electronics and electric vehicles, perform well, but are too expensive for widespread use on the grid because many batteries will be needed, and they will likely need to be large. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300^oC (572^oF), making them less energy efficient and safe than batteries that run at ambient temperatures.

The electrodes in lithium rechargeable batteries that interest scientists are made of manganese oxide. The atoms in this metal oxide form many holes and tunnels that lithium ions travel through when batteries are being charged or are in use. The free movement of lithium ions allows the battery to hold electricity or release it in a current. But there are problems with simply replacing the lithium ions with sodium ions because sodium ions are 70 percent bigger than lithium ions and don't fit in the crevices as well. So, the scientists needed to find a way to make the holes in the manganese oxide larger. They have done this by mixing different kinds of manganese oxides at different temperatures. The manganese oxide formed after mixing at 750^oC (1382^oF) created a material that had the best crystals, high capacity, and held up well to cycles of charging and discharging. Unfortunately, the scientists found that the faster they charged the sodium ion batteries, the less electricity these batteries could hold, and grid batteries need fast charging so they can collect as much newly made energy coming from renewable sources as possible.

Reference
Yuliang Cao, Lifen Xiao, Wei Wang, Daiwon Choi, Zimin Nie, Jianguo Yu, Laxmikant V. Saraf, Zhenguo Yang, Jun Liu. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Advanced Materials, 2011; DOI: 10.1002/adma.201100904

Further Reading
Oxidation and Reduction
Oxidation State (oxidation number)
Batteries and Fuel Cells
Trends in Atomic Radius

Study Questions

1. Explain what is meant when an electrochemist refers to
   • oxidation
   • reduction
   • redox
     
   
   
2. What do Chemists mean when they refer to
   
   • electrochemical cell
   • battery
   • primary cell
   • secondary cell
   
   
3. Write a balanced half-equation for each of the following:
   
   • oxidation of sodium atoms
   • oxidation of lithium atoms
   
   
4. The following compounds have been used as positive electrodes in lithium ion batteries:
   • LiCoO₂
   • LiMn₂O₄
   • LiNiO₂
   • LiFePO₄
   • Li₂FePO₄F
     
   For each of the compounds above, determine the oxidation state (oxidation number) of the transition metal in the compound.
   
   
   
5. Explain why sodium ions are larger than lithium ions.
6. Why is the size of the metal ion important in the functioning of the rechargeable batteries being discussed?
   
7. Could potassium ions be used instead of lithium ions in the rechargeable batteries under discussion? Explain your answer.
8. Could beryllium ions be used instead of lithium ions in the rechargeable batteries under discussion? Explain your answer.

Mammoth Collagen

University of York and Manchester scientists have extracted protein from the bones of a 600,000 year old mammoth. The scientists used an ultra-high resolution mass spectrometer to produce an almost complete sequence of amino acids for the collagen protein.

About 30% of all the protein found in mammals is collagen, making it the most abundant protein found in mammals. It is the main component of connective tissue and is found in muscles, tendons, ligaments and skin as well as in the cornea, cartilage, bone, blood vessels, the gut and intervertebral discs.

A collagen molecule can be about 300nm long and 1.5nm wide and is made up of 3 polypeptide chains in the structure of a left-handed helix. These helices twist together into a right-handed coil forming a triple helix which is stabilized by hydrogen bonds.
In each of the three polypeptide chains there is a regular arrangement of amino acids, often following the sequence Gly-Pro-X or Gly-X-Hyp where X is another amino acid.

Bio-archaeologists are excited about this because it is believed that protein can last in a useful form ten times longer than DNA. So, while DNA is useful in discoveries up to 100,000 years old, collagen could be used in identifying extinct animals up to 1,000,000 years old.

Reference
M. Buckley, N. Larkin, M. Collins. Mammoth and Mastodon collagen sequences; survival and utility. Geochimica et Cosmochimica Acta, 2011; 75 (7): 2007 DOI: 10.1016/j.gca.2011.01.022

Further Reading
http://www.ausetute.com.au/aminoacid.html
http://www.ausetute.com.au/proteins.html
http://www.ausetute.com.au/dna.html

Study Questions

1. What is the general name given to the smaller units that make up a protein?
2. Name the four elements found in all proteins.
   
3. What is meant by the term polypeptide?
4. Explain why proteins are considered to be biological polymers.
   
5. What is a peptide bond?
6. Amino acids are often represented by a three letter code. Give the name for each of the following amino acids:
   
   • gly
   • ala
     
   • hyp
   • pro
7. Draw a structure for each of the following tripeptides:
   
   • gly-ala-hyp
   • gly-pro-ala
8. Identify the peptide bond(s) in each of the tripeptides above.
9. What is meant by each of the following terms with respect to proteins:
   
   • primary structure
   • secondary structure
   • tertiary structure
10. Describe the primary, secondary and tertiary structures for collagen.
    

AUS-e-NEWS June 2011

People are fascinated by things that glow in the dark.
The June 2011 issue of AUS-e-NEWS takes at look at the chemistry of glow sticks.

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