Direction of Reversible Reactions
Introduced| English |
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| reversible reaction/rɪˈvɜːsɪbl rɪˈækʃn/ |
A two-way street
- Most reactions we meet run one way to completion.
- But many can run backward too, remaking their starters.
- A double arrow marks a reaction that goes both ways.
- Which way it leans depends on the conditions.
Forward and reverse
- A reversible reaction 可逆反应 can proceed in both directions.
- The forward reaction makes products; the reverse remakes reactants.
- We write it with a double arrow $\rightleftharpoons$.
The symbol $\rightleftharpoons$ in an equation means the reaction is...
A double arrow marks a reversible reaction.
Leaning one way
- Conditions push the balance toward products or toward reactants.
- Adding reactants drives it forward; adding products drives it back.
- The net direction is whichever is currently faster.
Adding more reactant to a reversible reaction shifts it toward...
Extra reactant speeds the forward reaction, making more products.
Adding a product to a system at equilibrium shifts the reaction...
Adding a substance drives the reaction away from it.
Settling into equilibrium
- As products build up, the reverse reaction speeds up.
- Eventually the two rates match and equilibrium sets in.
- The reaction then holds steady, leaning wherever it settled.
Which way will it go?
Compare the reaction quotient Q with K to predict the direction.
In a reversible reaction, only one direction ever runs at a time.
Both directions always run; the net change is the difference.
As products build up, the ____ reaction speeds up.
More product raises the reverse rate until it matches the forward.
If you add more reactant to a system at equilibrium, which way does it shift?
- More reactant speeds up the forward reaction.
- So the reaction shifts toward the products.
A single arrow ($\to$) usually means the reaction...
A single arrow shows a reaction that goes nearly all the way.
A double arrow ($\rightleftharpoons$) means reversible; a single arrow ($\to$) means it goes essentially to completion. The "direction" is the net change -- both reactions always run. And adding a substance drives the reaction away from that substance, toward the other side.
A reversible reaction ($\rightleftharpoons$) runs both forward (making products) and backward (remaking reactants). Conditions tip the net direction, and adding a substance pushes the reaction away from it. As products build, the reverse speeds up until the rates match at equilibrium.