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Oxygen 65% of Body Weight Oxygen is present in water and other compounds. Liquid oxygen in an unsilvered dewar flask. Liquid oxygen is blue. Warwick Hillier, Australia National University, Canberra Oxygen is necessary for respiration. You will find this element in the lungs, since about 20% of the air you breathe is oxygen.

99% of the mass of the human body is made up of only six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Every organic molecule contains carbon. Since 65-90% of each body cell consists of water (by weight), it isn't surprising that oxygen and hydrogen are major components of the body. Here's is a look at the major elements in the body and what these elements do. Carbon Carbon is found in every organic molecule in the body. Photograph of graphite, one of the forms of elemental carbon. U.S. Geological Survey Carbon is ingested in food that is eaten and breathed in as a component of air. It is found in the lungs as a waste product of respiration, carbon dioxide.

The Chemical Basis for Life Carbon is the basis for organic chemistry , as it occurs in all living organisms. Carbon is a nonmetal that can bond with itself and many other chemical elements , forming nearly ten million compounds . Elemental carbon can take the form of one of the hardest substances (diamond) or one of the softest (graphite). Carbon is made in the interiors of stars, though it was not produced in the Big Bang. Carbon compounds have limitless uses. In its elemental form, diamond is a gemstone and used for drilling/cutting; graphite is used in pencils, as a lubricant, and to protect against rust; while charcoal is used to remove toxins, tastes, and odors. The isotope Carbon-14 is used in radiocarbon dating. Carbon has the highest melting/sublimation point of the elements. The melting point of diamond is ~3550°C, with the sublimation point of carbon around 3800°C. Pure carbon exists free in nature and has been known since prehistoric time. The origin of the name 'carbo

Chemistry of Carbohydrates Carbohydrates or saccharides are the most abundant class of biomolecules. Carbohydrates are used to store energy, though they serve other important functions as well. This is an overview of carbohydrate chemistry, including a look at the types of carbohydrates, their functions, and carbohydrate classification. What Is a Carbohydrate? Carbohydrates are a common class of simple organic compouds. A carbohydrate is an aldehyde or a ketone that has additional hydroxyl groups. The simplest carbohydrates are called monosaccharides, which has the basic structure (C·H2O)n, where n is three or greater. Monosaccharides link together to form oligosaccharides and polysaccharides. Two monosaccharides link together to form a disaccharide. Functions of CarbohydratesCarbohydrates serve several biochemical functions: Monosaccharides are a fuel for celular metabolism. Monosaccharides are used in several biosynthesis reactions. Monosaccharides may be converted into space-saving

Introductory Stoichiometry A chemical equation describes what happens in a chemical reaction . The equation identifies the reactants (starting materials) and products (resulting substance), the formulas of the participants, the phases of the participants (solid, liquid, gas), and the amount of each substance. Balancing a chemical equation refers to establishing the mathematical relationship between the quantity of reactants and products. The quantities are expressed as grams or moles. It takes practice to be able to write balanced equations . There are essentially three steps to the process: Write the unbalanced equation. Chemical formulas of reactants are listed on the lefthand side of the equation. Products are listed on the righthand side of the equation. Reactants and products are separated by putting an arrow between them to show the direction of the reaction. Reactions at equilibrium will have arrows facing both directions. Balance the equation. Apply the Law of Conservation of

Tin oxide is heated with hydrogen gas to form tin metal and water vapor. Write the balanced equation that describes this reaction. Write the unbalanced equation. SnO2 + H2 → Sn + H2O Refer to Table of Common Polyatomic Ions and Formulas of Ionic Compounds if you have trouble writing the chemical formulas of the products and reactants. Balance the equation. Look at the equation and see which elements are not balanced. In this case, there are two oxygen atoms on the lefthand side of the equation and only one on the righthand side. Correct this by putting a coefficient of 2 in front of water: SnO2 + H2 → Sn + 2 H2O This puts the hydrogen atoms out of balance. Now there are two hydrogen atoms on the left and four hydrogen atoms on the right. To get four hydrogen atoms on the right, add a coefficient of 2 for the hydrogen gas. Remember, coefficients are multipliers, so if we write 2 H2O it denotes 2x2=4 hydrogen atoms and 2x1=2 oxygen atoms. SnO2 + 2 H2 → Sn + 2 H2O The equation is