The core of understanding chemical reactions with high-school chemistry is a chain of logical questions about "why, how, how, how, how, where." here is a system framework for you from five dimensions:
I. Energy perspective: why does the reaction occur
High school chemistry judge the spontaneousity of the reaction using argon (h) and entropy (s)。
Basis of judgement meaning examples
Heating reaction (Δh)
Entropy (Δs > 0) increased system confusion towards disorder, solid decomposition, increased gas molecules
Comprehensive testosterone (Δg=h-tΔs)
Elements of understanding: self-reaction does not mean rapid response. A lot of thermal reactions (e. G. Combination h2 and o2) need to be ignited before they can be activated, which suggests the feasibility of thermodynamics, the viability of kinetics。
From microstructures: how did the response happen
1. Breaking and formation of chemical keys
The essence of the chemical reaction is that the old key breaks and the new key is formed。
- ion reaction: reorganization of the ion in the solution, which is essentially a reorganization of the ion key (e. G. Ag+ + cl - → agcl↓)
- covalent reactions: break covalent keys are required, usually with higher energy (e. G. N2 + 3h2 ⇌ 2nh3, n≡n 3 keys are large and therefore high temperature and high pressure)
2. Electronic transfer perspective
Split the reaction into oxidizing and non-oxidizing reaction:
- oxidization: there is electronic transfer (or deviation) as measured by the rise or decrease in the compound price
- oxygen inoculation (high chemical amalgamation, electron loss, oxidation)
- fall back
- non-oxidized reduction: ion exchange is the essence of the decomposition reaction, without electronic transfer
Iii. In terms of speed: how fast is the response
Collision theory is the cornerstone of high school's understanding of response rates:
1. Reaction molecules must collide
2. Must be effective collisions (appropriate orientation)
3. Moleculars must have sufficient energy (ea)
This theory explains the factors that influence the rate:
- condensation ↑ number of molecules in unit volume ↑ impact frequency ↑
- temperature oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillator oscillant oscillator oscillator oscillator oscillator oscillator oscillator oscillation oscillator oscillary oscillary oscillator oscillation oscillor oscimen oscimenal osmology oscimenary osmography oscillation of ea
- catalyst, boom, change the response path, boom, drop the ea, boom, effective collision ratio, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom, boom
- pressure (gas) poignant to increase concentration
Iv. From a limit perspective: to what extent does the response take place
Reversible reactions are described by chemical balance:
- the lechartley doctrine: if a condition that affects the balance is changed, the balance moves in a direction that reduces the change
- temperature, boom, move in the direction of heat
- pressurize, boom, move to less gaseous molecules
- a reaction, um, moving in the direction of the generator (but the rate of conversion of the reaction is not necessarily higher)
Balance constant k is only related to temperature and quantitatively indicates the limits of the reaction. The bigger the k, the more thorough the reaction。
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V. From a taxonomy perspective: to create a map of the type of response
In high schools, chemical reactions are classified into four basic types, but the deeper understanding is that they are reclassified with oxidation:
Chemical reactions
Ideas - oxidation reaction (electronic transfer)
Ideas - replacement response (must)
│ ideas - polyincorporation/decomposition (generally yes)
│ - part of the complex response (e. G. Differentiation, integration)
└ - non-oxidized reaction (no electronic transfer)
Ideas - recomposition reaction (must be, condition: formation of sediment/gas/weak electrolyte)
└ - partially integrated/decomposition (e. G., cao + h2o = ca(oh)2)
Vi. A composite example: a full set of theoretical analyses of synthetic ammonia
Take the example of n2 + 3h2 ⇌ 2nh3:
Theoretical dimensions
Energy
The n≡n key is big, it's active, it needs high temperature and iron touchers to reduce ea
High pressure facilitates movement in the direction of a positive reaction
Industrial conditions 500 °c, 20-50 mpa, iron medium - best compromise between speed, balance, cost, not theory
Summary: the conceptual framework for understanding chemical reactions
Any chemical reaction can be considered in this order:
1. Nature: has there been a change in the combination price? • to determine whether it is oxidized or not
2. Energy: the positive and negative of tha? Well, let's see
3. Looking at microlevels: what's broken? What's the key? ♪ understand the response machine ♪
4. Conditional: how does temperature/pressure/catalyst affect? ~ distinguishing speed and balance
5. Results: reversible? K-value size? • determination of conversion and yield rates
The framework integrates seemingly fragmented knowledge points (thermal chemistry, speed balance, electrochemicals, structural chemistry) in high-school chemistry into an organic whole。
