衝突頻度、触媒および平衡選択
導入済み| English | 意味 |
|---|---|
| equilibrium/ˌiːkwɪˈlɪbrɪəm/ | 平衡 |
| catalyst/ˈkætəlɪst/ | 触媒 |
| activation energy/ˌæktɪˈveɪʃn ˈenədʒi/ | 活性化エネルギー |
| tangent/ˈtændʒənt/ | 接線 |
Why can the fastest conditions give a poorer yield?
- An industrial reaction must make product quickly and give enough product at equilibrium 平衡. A hotter reactor can speed an exothermic reaction while reducing its equilibrium yield.
- Separate collision frequency, molecular energy and equilibrium position before deciding which change helps. A catalyst 催化剂 changes the route and the time to equilibrium, not the equilibrium yield at fixed conditions.
Explain successful collisions
- Reaction requires collisions with suitable orientation and enough energy to overcome activation energy 活化能. At fixed temperature, higher concentration or gas pressure makes collisions more frequent; a larger exposed solid surface provides more accessible reaction sites.
- Increasing temperature gives more frequent collisions and, especially, a larger fraction with enough energy. On equal-particle-number energy distributions, the hotter curve is broader with a lower peak and more area beyond the same activation-energy threshold; total area stays the same.
反応ガスが一定温度下で圧縮される。collision theory（衝突理論）に基づき、どの記述が支持されるか？
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粒子間距離が短くなり衝突頻度が増加する。一定温度ではエネルギー分布が維持されるため、圧縮だけでは高エネルギー分子の割合は増加しない。
Measure a rate at the stated time
- For the same fixed endpoint, relative rate is proportional to $1/t$: 20 s versus 50 s gives rate ratio $(1/20)/(1/50)=2.5$. This comparison assumes the same endpoint amount and matched conditions.
- For gas volume against time, draw a tangent 切线 at the requested point and choose two well-separated points on that tangent. Points (20 s, 30 cm³) and (60 s, 50 cm³) give gradient $\dfrac{50-30}{60-20}=0.50\,\dfrac{\mathrm{cm}^3}{\mathrm s}$. The line from the origin to P gives an average rate, not the instantaneous tangent rate.
With equal endpoint amounts, a halogenoalkane taking 5 s has 36 times the relative rate of one taking 180 s: (1/5)/(1/180) = 36. An endpoint comparison does not prove a complete rate law or isolate bond strength if other conditions differ.
2つの対応する実験が 15 s と 45 s で同じ到達点に達する。15 s の実験の相対反応速度を、45 s の実験のそれで割った値を計算せよ。
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同じ到達点量に対して、相対反応速度は 1/時間 に比例する。比 = (1/15)/(1/45) = 45/15 = 3。
気体体積曲線の接線は (10 s, 25 cm³) と (50 s, 49 cm³) を通る。その勾配を cm³ / s で求めよ。
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勾配 = 体積変化/時間変化 = (49 − 25)/(50 − 10) = 24/40 = 0.60 cm³ / s。原点から曲線への接線ではなく、接線上の点を使用せよ。
Change the route without changing the energy distribution
- At fixed temperature, a catalyst gives an alternative route with lower activation barriers; the molecular-energy distribution itself stays unchanged. More particles can react, and both forward and reverse reactions become faster.
- Draw catalysed and uncatalysed reaction profiles with the same start/end levels and ΔH. A two-step catalysed route has two peaks and an intermediate valley. A selective route can improve atom economy; faster operation may use less energy, but neither benefit is guaranteed for every catalyst.
一定温度において、触媒は平均分子エネルギーを増加させることで生成物の平衡濃度を上げる。
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触媒は温度分布を変化させずに経路の障壁を下げる。両方向の速度を速め、一定条件では平衡位置と平均エネルギーは変わらない。
Justify equilibrium shifts and a numerical compromise
- In a closed system at dynamic equilibrium, forward and reverse rates are equal and concentrations stay constant; concentrations need not be equal. For N₂(g) + 3H₂(g) ⇌ 2NH₃(g), increasing pressure favours fewer gas moles, and adding N₂ favours its consumption. For an exothermic forward reaction, cooling favours products but slows reaction.
- Supplied plant data at 450, 550 and 650 K give yields 92%, 76%, 46% and relative rates 0.040, 0.60, 2.5. If yield must be at least 70% and rate at least 0.50, only 550 K meets both. These requirements justify that choice; the table alone does not establish a global economic optimum.
Pressure does not shift equilibrium when the two gas sides have equal mole totals. A catalyst does not favour products at equilibrium. Constant concentration means continuing reactions balance, not that molecular reactions stop.
Use collision theory for rate, tangent or fixed-endpoint data for measurement, and reversible-reaction reasoning for yield. Test industrial choices against the actual numerical constraints.
450/550/650 K における収率は 92/76/46% 、相対反応速度は 0.040/0.60/2.5 である。収率 ≥70% かつ速度 ≥0.50 を満たすのはどれか？
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450 K は速度制限を満たさない；650 K は収率制限を満たさない。550 K のみが両方を満たす。提示された制限は普遍的な経済的最適点を定義するものではない。