How to Control Chemical Reactions
Most chemical reactions carried out in the chemistry laboratory are uneventful. Some reactions are quite dangerous. Sometimes even an ordinarily dangerous reaction can be controlled in such a way it is not a problem.
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Instructions
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Recognize the causes of runaway reactions. Although there are some rare causes for a reaction to get out of control, ordinarily a reaction is dangerous for one of two reasons. One reason is a sudden release of gas during the course of reaction. The second reason is the sudden release of heat.
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2
Avoid unseen dangers. Static electricity, perhaps from stirring or touching a reaction vessel, can set off an explosion. Explosives convert from solid or liquid to gases, instantaneously. An example is TNT. Another is nitroglycerin.
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3
Decide how you will combine reagents. It is well known that water should not be poured into sulfuric acid. Why? The liquid can splatter all over the person doing the pouring. This can lead to horrible burns and blindness. What causes the liquid to splatter? A tremendous release of energy as heat makes the liquid instantly boil out of control.
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4
Determine the quantities of chemicals involved and if you need to add a reagent gradually. A gallon of reactants is considerably more dangerous than an eyedropper full of them. One way to accomplish a reduction is to very slowly drip one reactant into the complete amount of the other reactant, perhaps with rapid stirring. The reaction requires both reactants, so only a small reaction is occurring at any moment. Heat generated is quickly dispersed, and gas generated is minimal.
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Determine whether a solvent is called for. By combining one or more of the reactants in a large volume of solvent, the number of reactant molecules coming together in a unit of time is greatly decreased by dilution.
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Tips & Warnings
Consider cooling the reagents before and during the reaction to help avoid excess heat. Vessels can be cooled with ice water, dry-ice and alcohol, or liquefied gases, as necessary.
Research a reaction well in advance, and anticipate what could go wrong. This is especially important in organic chemistry, as rearrangement reactions can produce compounds considerably different from those anticipated.
