Skip to main content

Stoichiometry

 Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical  reactions.

Stoichiometry was founded on the law of conservation of mass where the total mass of the reactants equals the total mass of the products, leading to the insight that the relations among qualities of reactants and products typically form a ratio of positive integers. This means that if the amounts of separate reactants are known, then the amount of the product can be calculated. Conversely, if one reactant has a known quantity and the quantity of the products can be empirically determined, then the amount of other reactants can also be calculated.


This is illustrated in this example, where the balanced equation is:

         CH4 + 2O4 -----> CO2 + 2H2O

Here, one molecule of methane reacts with two molecules of oxygen gas to yield one molecule of carbon dioxide and two molecules of water. This particular chemical reaction is an example of complete combustion. Stoichiometry measures these quantitative relationships, and is used to determine the amount of products and reactants that are produced or needed in a given reaction. Describing the quantitative relationships among substances as they participate in chemical reactions is known as reaction stoichiometry. In the example above, reaction stoichiometry measures the relationship between the quantities of methane and oxygen that react to form carbon dioxide and water.

Because of the well known relationsgip of moles to atomic weights, the ratios that are arrived at by stoichiometry can be used to determine quantities by weight in a reaction described by a balanced reaction. This is called composition stoichiometry.

Gas stoichiometry deals with reactions involving gases, where the gases are at a known temperature  pressure, and volume and can be assumed to be ideal gases. For gases, the volume ratio is ideally the same by the ideal gas law, but the mass ratio of a single reaction has to be calculated from the molecular gases of the reactants and products. In practice, due to the existence of isotopes, molar masses are used instead when calculating the mass ratio.

x--------x

This Chapter is sponsored by K-Swiss.

Comments

Popular posts from this blog

How to Create a Richly Imagined World

For someone who likes fantasy and sci-fi fiction, most of the time, a lot of people ask me about how to create a richly imagined world. Fantasy and sci-fi elements rest heavily on how an author weave the setting and the world in which the heroes dwell in, and it helps to make the novel to be imagined vividly in the readers' minds. A convincing world should be relatable, something that we can associate ourselves with. For us to be associated with a world an author created in his mind, and wrote on the pages of a book, this world has to be close to the real thing. It has to be systematic, real and alive, and very convincing. A real world has certain elements, and an author must consider them in writing a vividly imagined world: Cartography - a fantasy or sci-fi world depend heavily on geography and maps, especially if the plot requires war and the belligerents occupy so much space in the plot. A convincing world has the world separated in territories, and every part of the...

Simple Machine

A simple machine is a mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. Usually the term refers to the six classical simple machines that were defined by Renaissance scientists: Lever Wheel and axle Pulley Inclined plane Wedge Screw A simple machine uses a single applied force to do work against a single work load. Ignoring friction losses, the work done on the load is equal to the work done by the applied force. The machine can increase the amount of the output force, at the cost of a proportional decrease in the distance moved by the load. The ratio of the output to the applied force is called the mechanical advantage. Simple machines can be regarded as the elementary "building blocks" of which all more complicated machines (sometimes called compound machines) are composed. For example, wheels, levers, and pulleys are all use...

Mariology

 Mariology is the theological study of Mary, the mother of Jesus. Mariology seeks to relate doctrine or dogma about Mary to other doctrines of the faith, such as those concerning Jesus and notions about redemption, intercession, and grace. Mariology aims to place the role of the historic Mary in the context of scripture, tradition and the teachings of the Church on Mary. In terms of social history, Mariology may be broadly defined as the study of devotion to and thinking about Mary throughout the history of Christianity.  There exist a variety of Christian (and non-Christian) views about Mary as a figure ranging from the focus on the veneration of the Blessed Virgin Mary in Roman Catholic Mariology to criticisms of "mariolatry" as a form of idolatry. The latter would include certain Protestant objections to Marian devotion. There are also more distinctive approaches to the role of Mary in Lutheran Marian theology and Anglican Marian theology. As a field of theology, the most ...