Dynamic equilibrium: equal rates, continuing reactions
도입됨| English | 의미 |
|---|---|
| reversible reaction/rɪˈvɜːsɪbl rɪˈækʃn/ | 가역 반응 |
| equilibrium/ˌiːkwɪˈlɪbrɪəm/ | 평형 |
What would explain this observation?
- A closed reaction vessel can show constant composition while particles still react in both directions. Equality of rates keeps the overall amounts unchanged.
Build the model
- When a reversible reaction 可逆反应 occurs in apparatus preventing escape of reactants and products, equilibrium 平衡 is reached when forward and reverse reactions occur at exactly the same rate.
- The state is dynamic: both directions continue.
- At fixed conditions the amounts of reactants and products stay constant, but they need not be equal.
- A closed system prevents loss of matter; it does not necessarily prevent energy transfer to maintain a set temperature.
- equilibrium: A state with equal forward and reverse reaction rates.
- reversible reaction: A reaction whose products can react to reform the original reactants.
Equal rates do not require equal amounts
$A\rightleftharpoons B$
In this closed A ⇌ B model, a catalyst changes how quickly equilibrium is reached, not its final composition.
Which pair must be equal at dynamic equilibrium?
난이도 1/5 · 100 코인 + 오늘 첫 완료 시 소액 보너스
Equilibrium is dynamic: forward and reverse reactions continue at EQUAL RATES, so concentrations stay constant. The concentrations themselves are usually unequal, and equal masses are irrelevant.
Match each technical term to its precise meaning.
난이도 2/5 · 140 코인 + 오늘 첫 완료 시 소액 보너스
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Beginning with mostly reactants, the forward rate may be high while the reverse rate is initially low.
- As products accumulate, reverse reaction becomes possible more often until the rates match under the stated model.
- A reaction-rate graph should show convergence to the same non-zero rate.
- A composition graph can level off at different reactant and product amounts.
- Identify which quantity is on the axis before claiming two curves must meet.
In the lab: Use an original particle-count model or supplied data with fixed conditions and no matter lost. Count forward and reverse events over equal time windows. Their difference gives net change for a one-to-one A ⇌ B model. Do not build a sealed heated chemical apparatus to demonstrate the idea; safe school demonstration arrangements require approved containment and temperature control. A count model illustrates balance without proving a particular real chemical rate law.
Which two habits make the investigation or model in this case more defensible?
난이도 2/5 · 140 코인 + 오늘 첫 완료 시 소액 보너스
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: in a closed A ⇌ B model, 18 forward and 18 reverse events occur in one second.
- Net B change=18−18=0 even though 36 reaction events occur.
- If 70 A and 30 B particles remain on average, these unequal amounts are compatible with equilibrium.
- At an earlier interval with 20 forward and 12 reverse events, net B increases by eight and the model is not yet at equilibrium.
Your turn: In a one-to-one A ⇌ B model, 22 forward and 22 reverse events occur in one second. Find net change in B count.
In a one-to-one A ⇌ B model, 22 forward and 22 reverse events occur in one second. Find net change in B count.
난이도 2/5 · 140 코인 + 오늘 첫 완료 시 소액 보너스
The result is 0 particles. Known: 22 forward and 22 reverse events per second in a 1:1 A-B model. Net change in B = forward - reverse = 22 - 22 = 0 particles per second. Thirty-six events occur while the count stands still - that is "dynamic".
Check the conclusion and its limits
- Constant amounts do not mean particles are motionless or reaction has stopped.
- A steady open-flow system can also have constant measured amounts, so constancy alone does not establish closed-system equilibrium.
- Equal mass, concentration and molecule count are not the required equality: rates are.
- Condition-change predictions are separately Higher-only.
Not true: At dynamic equilibrium both chemical reactions have stopped. Dynamic equilibrium means the reactions keep running in both directions at matching rates. Everything continues at the particle level; only the observable NET change is zero.
- When a reversible reaction occurs in apparatus preventing escape of reactants and products, equilibrium is reached when forward and reverse reactions occur at exactly the same rate.
- Beginning with mostly reactants, the forward rate may be high while the reverse rate is initially low.
- Watch for: constant amounts do not mean particles are motionless or reaction has stopped.
At dynamic equilibrium both chemical reactions have stopped.
난이도 1/5 · 100 코인 + 오늘 첫 완료 시 소액 보너스
Dynamic equilibrium means the reactions keep running in both directions at matching rates. Everything continues at the particle level; only the observable NET change is zero.
A state with equal forward and reverse reaction rates: write the technical term.
난이도 1/5 · 100 코인 + 오늘 첫 완료 시 소액 보너스
equilibrium means A state with equal forward and reverse reaction rates.