News tagged with chemical composition
Physicists investigate structural properties of spider webs
(PhysOrg.com) -- "Although the orb web of a spider is a lightweight structure, it seems to be a highly optimized structure, presumably as a result of evolution from the Jurassic period or earlier," explain ...
Feb 08, 2010 |
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Astronomers watch instant replay of powerful stellar eruption
Astronomers are watching the astronomical equivalent of an instant replay of a spectacular outburst from the unstable, behemoth double-star system Eta Carinae, which was initially seen on Earth nearly 170 ...
Feb 15, 2012 |
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Cockroach 'let's hook up' chemical signal could benefit endangered woodpecker
A North Carolina State University discovery of the unique chemical composition of a cockroach signal -- a "Let's hook up" sex pheromone emitted by certain female wood cockroaches to entice potential mates ...
Dec 19, 2011 |
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First comet found with ocean-like water: New clues to creation of Earth's oceans
(PhysOrg.com) -- New evidence supports the theory that comets delivered a significant portion of Earth's oceans, which scientists believe formed about 8 million years after the planet itself.
Space & Earth / Space Exploration
Oct 05, 2011 |
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Messenger orbital data confirm theories, reveal surprises
On March 18, 2011, the MESSENGER spacecraft entered orbit around Mercury to become that planet's first orbiter. The spacecraft's instruments are making a complete reconnaissance of the planet's geochemistry, ...
Space & Earth / Space Exploration
Jun 16, 2011 |
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Clues to Neanderthal hunting tactics hidden in reindeer teeth
Scientists have found that our cousins the Neanderthal employed sophisticated hunting strategies similar to the tactics used much later by modern humans. The new findings come from the analysis of subtle chemical ...
Other Sciences / Archaeology & Fossils
May 16, 2011 |
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Algae and bacteria hogged oxygen after ancient mass extinction, researchers say
(PhysOrg.com) -- After the biggest mass extinction in Earth's history -- 250 million years ago -- ocean algae and bacteria rebounded so fast that they consumed virtually all the oxygen in the sea, slowing ...
Space & Earth / Earth Sciences
Mar 25, 2011 |
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Plasmonic metamaterials: From microscopes to invisibility cloaks
(PhysOrg.com) -- A new class of artificial materials called metamaterials -- which derive their properties from carefully engineered, nanostructured building blocks rather than from their chemical composition ...
Jan 21, 2011 |
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Meteorite just one piece of an unknown celestial body
(PhysOrg.com) -- Scientists from all over the world are taking a second, more expansive, look at the car-sized asteroid that exploded over Sudan's Nubian Desert in 2008. Initial research was focused on classifying ...
Space & Earth / Space Exploration
Dec 15, 2010 |
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Super-Earth has an atmosphere, but is it steamy or gassy?
In December 2009, astronomers announced the discovery of a super-Earth known as GJ 1214b. At the time, they reported signs that the newfound world likely had a thick, gaseous atmosphere. Now, a team led by ...
Dec 01, 2010 |
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Plants kick-start evolutionary drama of Earth's oxygenation
An international team of scientists, exploiting pioneering techniques at Arizona State University, has taken a significant step toward unlocking the secrets of oxygenation of the Earth's oceans and atmosphere.
Space & Earth / Earth Sciences
Oct 08, 2010 |
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Avoid swimming in interplanetary lakes: Research confirms oily 'water' on Saturn's moon
Titan, one of Saturn's moons, is the only moon in the solar system with an atmosphere -- ten times denser than the atmosphere of Earth. Five years ago, the Cassini-Huygens mission to Saturn, a collaboration ...
Space & Earth / Space Exploration
Sep 21, 2010 |
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Phoenix Mars Lander finds surprises about red planet's watery past
(PhysOrg.com) -- Liquid water has interacted with the Martian surface throughout Mars' history, measurements by NASA's Phoenix Mars Lander suggest.
Space & Earth / Space Exploration
Sep 09, 2010 |
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Variations in fine-structure constant suggest laws of physics not the same everywhere
(PhysOrg.com) -- One of the most controversial questions in cosmology is why the fundamental constants of nature seem fine-tuned for life. One of these fundamental constants is the fine-structure constant, ...
Sep 06, 2010 |
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New insights into how stem cells determine what tissue to become
Within 24 hours of culturing adult human stem cells on a new type of matrix, University of Michigan researchers were able to make predictions about how the cells would differentiate, or what type of tissue ...
Aug 01, 2010 |
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Empirical formula
In chemistry, the empirical formula of a chemical compound is a simple expression of the relative numbers of each type of atom in it, or the simplest whole number ratio of atoms of each element present in a compound. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The empirical formula is used as standard for most ionic compounds, such as CaCl2, and for macromolecules, such as SiO2. The term empirical refers to the process of elemental analysis, a technique of analytical chemistry used to determine the relative amounts of each element in a chemical compound.
In contrast, the molecular formula identifies a numbers of each type of atom in a molecule, and the structural formula also shows the structure of the molecule.
For example, the chemical compound n-hexane has the structural formula CH3CH2CH2CH2CH2CH3, which shows that it has 6 carbon atoms arranged in a straight chain, and 14 hydrogen atoms. Hexane's molecular formula is C6H14, and its empirical formula is C3H7, showing a C:H ratio of 3:7. Different compounds can have the same empirical formula. For example, glucose, formaldehyde and acetic acid have the same empirical formula, CH2O. This is the actual chemical formula for formaldehyde, but acetic acid has double the number of atoms and glucose has six times the number of atoms.
For more information about Empirical formula, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
