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I don't understand the concept of dynamic equlibrum and it shifting right and left depending on pressure concentration and temperature

User Nikhil Baliga
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1 Answer

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6 votes

Answer:

See below.

Step-by-step explanation:

A dynamic equilibrium in chemistry refers to a situation in which the reaction of reactants to form product(s) in which the products can reverse the reaction by falling apart and back to the reactants. Reactions that go to completion are irreversible. In cases where reactants form products (in a forward reaction), but the products can change back into reactants (in a reverse reaction) are called reversible.

An example is the reaction of carbon dioxide with water to form carbonic acid (think soft drinks).

CO2(g)+H2O(l) ⇌ H2CO3(aq)

As anyone who has opened a warm can of soda knows, it can erupt suddenly and spray anyone nearby with a shower of bubbly, and sticky, soda. Carbonic acid is unstable and will happily decompose back to it's reactant molecules if given the chance.

Experience tells us what to expect when giving a brother or sister a can of warm soda that you've shaken hard for a minute. But if you are a chemist, such responses aren't always easy to predict with a new reaction. Equilibrium constants were developed to provide a means for presdicting the exstent of these reactions. They are used in equilibrium equations to predict the concentrations of products and reactants, given conditions of temperature and pressure, under defined conditions of temperature and pressure.

The equations themselves include concentrations as the key input. In the carbonic acid example, if one were to add excessive amounts of one of the reactants, one would expect the equilibrium to "shift to the right." This simply means that more carbonic acid would be made. The chances of the forward reaction increase as concentration increases. The amount of CO2 given off as a gas depends on the concentration of the CO2 in the gas phase, which is given by the partial pressure of the gas.

The space above the soda and the cap represents one place that the CO2(g) can escape the solution. The CO2 pressure in the gas phase is a measure of it's concentration. An equilbium calculation takes this concentration in account when decidng how much much of each component is present. Other compouns that are present may also impact the equilibrium since they may interfere with one of the reaction steps. Pressure and emperature either dirctly impact the concentration (e.g., gases) or they affect the "effective" concentrations of the compunds. A higher temperature creates more collisons between reactant molucules that may change the equilibrium constant..

User Geowar
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