How Does A System At Equilibrium Respond To The Addition Of More Reactant? More Product?


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James Kent Profile
James Kent answered
The chemistry question that you are asking relates to Le Chatelier’s Principle. Basically, if you add more reactant to the equation, then the position of equilibrium will shift towards the products in order to balance out the changes. Therefore adding more products will shift the equilibrium towards the reactants in order to balance it out.

Le Chatelier’s Principle states that if a chemical system at equilibrium experiences a change in concentration, temperature, volume or partial pressure, then equilibrium shifts to counteract the imposed change and a new equilibrium is established.

As mentioned in the definition above, there are a number of factors that can cause a change in the equilibrium of a chemical reaction. Each one of these changes can have a different effect.
If there is a change in the concentration of an ingredient in the equilibrium equation, then the equilibrium will shift to the side that would reduce the effects of that change in concentration.

The effect of a change in temperature is a little more complicated. When the reaction is exothermic (heat energy is given out) then we include the heat as a product, which means that equilibrium would shift towards the reactants. If the reaction is endothermic (heat energy is taken in) then we would include the heat as a reactant, which means that the equilibrium would shift towards the products.

A change in pressure would cause the equilibrium to shift towards the side of the equation which contains the least moles. For example, the reaction of nitrogen gas with hydrogen gas to form ammonia N2 + 3 H2 ⇌ 2 NH3. There are four moles present on the left side of the equation, and two on the right side, which means that equilibrium would shift towards the right to produce more product i.e. Ammonia.

And finally, if a catalysts is added to the equation, then it is important to remember that there would be no change in the equilibrium as both sides of the reaction would be speeded up, meaning that the reaction occurs more quickly.
Anonymous Profile
Anonymous answered
You want to look up Le Chatelier's Principle for details:
Basically adding more reactant shifts the equilibrium so the amount of product increases to take up the added ingredients and establish a new equilibrium.  Adding product increase the amount of reactants and establishes a new equilibrium.

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