Introduction This article reviews the technological use of exothermic chemical reactions that release their energy in a very short time interval. There are three primary fields of application for these effects:
To distinguish chemical changes from physical changes. To write chemical equations to describe a chemical reaction. To balance chemical equations. To calculate the quantities of reactants required or the quantities produced in a chemical reaction.
Chemical Reaction Equations Changes in a material or system are called reactions, and they are divided into chemical and physical reactions.
Energy is the driving force of all changes, both physical and chemical reactions. Energy is always involved in these reactions. If a system is more stable by losing some energy, a reaction takes place, releasing energy. Such a reaction is said to be exothermic. Supplying energy to a system also causes a reaction.
Energy absorbing reactions are called endothermic reactions. Sometimes, the amount of energy involved in a reaction may be so small that the change in energy is not readily noticeable. An equation can be used to describe a physical reaction, which involves a change of states.
For example, melting, sublimation, evaporation, and condensation can be represented as follow. Is the phase transition between graphite and diamond is a chemical or physical reaction? The crystal structures of diamond and graphite are very different, and bonding between the carbon atoms are also different in the two solid states.
Because chemical bonds are broken and new bonds are formed, the phase transition of diamond and graphite is a chemical reaction. Chemicals or substances change converting to one or more other substances, and these changes are called chemical reactions.
At the molecular level, atoms or groups of atoms rearrange resulting in breaking and forming some chemical bonds in a chemical reaction. The substances undergoing changes are called reactants, whereas substances newly formed are called products.
Physical appearances of products are often different from reactants. Chemical reactions are often accompanied by the appearance of gas, fire, precipitate, color, light, sound, or odor. These phenomena are related to energy and properties of the reactants and products.
This balanced reaction equation shows that five moles of oxygen reacts with one mole of propane generating three moles of carbon dioxide and four moles of water, a total of 7 moles of products in the combustion reaction. At the molecular level, this equation shows that for each propane molecule, 5 oxygen molecules are required.
The three carbon atoms are converted to three molecules of carbon dioxide, whereas the 8 hydrogen atoms in propane are oxidized to 4 water molecules. The numbers of H, C, and O atoms are the same on both sides of the equation. We study properties of substances so that we know how to make use of them.
Tendencies of a substance to react, either by itself or with others, are important chemical properties. Via properties, we understand chemical reactions, which are best studied by experimentation and observation. After you have performed many experiments, you may generalize certain rules and facts.
Knowing these rules and facts enable you to solve problems that you have not yet encountered. The most important aspect of a chemical reaction is to know what are the reactants and what are the products.
For this, the best description of a reaction is to write an equation for the reaction. A chemical reaction equation gives the reactants and products, and a balanced chemical reaction equation shows the mole relationships of reactants and products.
Often, the amount of energy involved in the reaction is given. Dealing with the quantitative aspect of chemical reactions is called reaction stoichiometry. This reaction is represented by the reaction as depicted in the picture, and the equation of the reaction is written as: Amounts of substances represented by chemical formulas have been introduced on the two previous pages, and these concepts should help to figure out the stoichiometry of reactions when a reaction equation is given.Welcome to CAcT, ©[email protected] Reaction Equations Key terms Energy, exothermic reaction, endothermic reaction Physical reactions, chemical reactions, phase .
Laboratory biosafety manual. Third edition World Health Organization Geneva WHO Library Cataloguing-in-Publication Data World Health Organization. For this new edition, the manual has been extensively revised and expanded. The manual now covers risk assessment and safe use of recombinant DNA technology, and provides guidelines for the comissioning and cetification of laboratories.
C From Masses to Balanced Equations: Page No. 1. State what we mean by a limiting reactant in a chemical reaction. [1 mark] Answer. The limiting reagent in a chemical reaction is the substance that is totally consumed when the .
Set 3 of mole calculations - deducing a balanced symbol equation from the masses of reactants and products. Since you can interpret equations in terms of moles and masses of reactants and products, you can also work in the other direction. Contents.
Introduction; Reactions and Heat; Black Powder; Fulminate; High Explosives; Smokeless Powder; Aromatic Explosives; Pyrotechnics; Fireworks; Safety; References.