In chemistry, a very important and widely used term is chemical equilibrium. If ever you decide to take a test on chemistry, that is used to show your competance in the subject, equilibrium will be a big part of it.
Well, now you know that equilibrium is important, but what is it? Well, equilibrium is when the forward rate of a reaction is equal to the reverse rate of a reaction. Huh? Well, lets explain this one with an example. Suppose we take hydrogen (H2) and oxygen (O2) and mix them together. Of course, they form water. the reaction of 2 H2 + O2 -----> 2H2O, is the forward reaction, but at the same time, H2O is decomposing into H2 and O2. This is the reverse reaction. So, when the rate of the forward reaction (2H2 + O2 -----> 2H2O) and the rate of the reverse reaction (2 H2O -----> 2 H2 + O2) are equal, then we have acheived equilibrium
Once equilibrium is reached, does everything just stop? No, actually, each reaction (both forward and reverse) keep going. Basically in our last example, the amount of H2 and O2 produced from the decomposition of water balances out with the amount of H2 and O2 that was used up to produce the same amount of water that was just used up. (Remember, the rates of reaction are the same, so the same amount of products and reactants are used up as they are produced again. This is an important fact to understand, because teachers love to ask this question a lot.)
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Unit 7 - Section 2