staychemical reactionThe substance that can participate in the reaction is called reactant, which refers to the substance that can be consumed in a chemical reaction.chemical reactionThe solvents and catalysts involved are not counted as reactants.
Chinese name
reactant
Foreign name
Reactant
Interpretation
staychemical reactionMedium, substance that can participate in the reaction
staychemical reactionThe substance that can participate in the reaction is called reactant. (In biology, it is called substrate or acceptor)chemical reactionA substance that can be consumed in.Although solvents and catalysts are generally involved in chemical reactions, they are not usually counted as reactants.
Reagents emphasize a specific use of this chemical.
Relevant information
Write thisIonic equationFirst of all, it is necessary to find out the ratio of reactants. If the ratio is not told, it is necessary to find out the order of dropping.Generally speaking, the reactant in the dropper is not enough when starting to drip, while the conical flask (or beaker, etcReaction vessel）Excessive reactants in.aboutNeutralization reactionFor example, if the alkali is excessive, the neutralization product isOrthosalt, if acid orAcid gasIn case of excessive reaction with alkali, it may generateAcid salt(YesPolybasic acidFor).stayRedox reactionMedium, ifOxidantIn case of excess, all elements that can be oxidized will be oxidized;If the oxidant is insufficientReducibilityStrong elements are oxidized first, like CltwoAnd FeBrtwoThe solution reacts like that.
Related reactions
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A reaction in which the product can continue to react with the excess reactant
Example 1. COtwoInject excessive NaOH solution: COtwo+2OH-=COthree2-+HtwoO
Excess CO2 into NaOH solution: COtwo+OH-=HCOthree-
Example 2: A small amount of NaOH solution is dropped into AlCl3 solution to react with Al3++3OH－=Al(OH)three↓
Small amount of AlClthreeSolution dropping into NaOH solution reaction: Al3++4OH－==AlOtwo－+2HtwoO
Example 3. FeClthreeSolution and NatwoS solution reaction
Fe3+And S2－Can occurRedox reactionGenerate Fe2+, while Fe2+And S2－It can react to generate FeS precipitation, which is soluble in acid solution, so it writes the ion reactionequationHigh attention should be paid to.
(1) When n (FeClthree)∶n(NatwoS) ≥ 2:1, namely FeClthreeSufficient, when the solution is acidic.
2Fe3++S2－=2Fe2++S↓
(2) When n (FeClthree)∶n(NatwoS) ≤ 2:3, i.e. NatwoS sufficient, when the solution is alkaline.
2Fe3++3S2－=2FeS↓+S↓
(3) When n (FeClthree）When: n (Na2S)=1 ∶ 1, Na2S and FeCl3 react completely.
① Determine whether a certain reactant is insufficient, excessive or appropriate according to the dosage ratio of reactants.
② Determine whether the product reacts with excessive reactants.
Special reaction
SomeIonic reactionIn addition to the relationship between the amount of reactants, other special factors should be considered to correctly write the ionic reactionequation。
Example 1. Newly prepared chlorine water and FeBrtwoSolution reaction
In addition to the relationship between the amount of reactants, the reaction should also consider the relationship between Fe2+and Br -ReducibilityStrength.Because Fe2+ReducibilityBetter than Br －, so CltwoPre oxidized Fe2+, post oxidation Br－。
(1) When n (FeBrtwo)∶n(Cltwo）≥ 2:1, i.e. FeBrtwoA small amount of chlorine water is dropped into the solution reaction.
2Fe2++Cltwo=2Fe3++2Cl－
(2) When n (FeBrtwo)∶n(Cltwo）≤ 2:3, i.e. FeBrtwoDrop sufficient chlorine water into the solution reaction.
2Fe2++4Br－+3Cltwo=2Fe3++2Brtwo+6Cl－
(3) When 2 ∶ 3<n (FeBrtwo)∶n(Cltwo）<2:1, for example, to 20mL0.1mol/L FeBrtwoFill the solution with 44.8mL chlorine under standard conditions.First, calculate n (FeBrtwo)∶n(Cltwo）=1 ∶ 1, and then write the ion reactionequation。
2Fe2++2Br－+2Cltwo=2Fe3++Brtwo+4Cl－
Note: Newly madeChlorine waterAnd FeItwoSolution reaction;Because I -ReducibilityRatio Fe2+Strong, so CltwoPre oxidation I－, post oxidized Fe2+。
Example 2. Mg (HCOthree)twoSolution reacts with NaOH solution
In addition to the relationship between the amount of reactants, ① Mg (OH)twoOfsolubilityRatio MgCOthreeThe solubility of is smaller, and the precipitate generated after reaction is Mg (OH)twoNot MgCOthree。②OH - reacts with Mg2+first and then with HCO3 -.
(1) When n [Mg (HCOthree)two]When: n (NaOH) ≤ 1:4, NaOH is sufficient.
Mg2++2HCOthree－+4OH－=Mg(OH)two↓+2COthree2－+2HtwoO
(2) When n [Mg (HCOthree)two]When: n (NaOH) ≥ 1 ∶ 2, that is, a small amount of NaOH.
Mg2++2OH－=Mg(OH)two↓
(3) When 1:43) 2]: n (NaOH) ≤ 1:3, such as n [Mg (HCOthree)two]∶n(NaOH) =1∶3
Mg2++HCO3－+3OH－=Mg(OH)two↓+COthree2－+HtwoO
(4) When 1 ∶ 3<n [Mg (HCOthree)two]When: n (NaOH)<1:2, such as n [Mg (HCOthree)two]∶n(NaOH) =5∶12
To sum up: different ionic reactions with different reactant dosage ratioequationThe writing of should be based on the nature of ions, the amount of reactants and the specific analysis of the reaction environment, and flexible use can be written correctly.
Speculative product
First, remember some colored substances or substances with special properties, which are often the starting point for solving problems, such as red: Cu;Cu2O；Red phosphorus (dark red), FetwoOthree(brownish red), Fe (OH)three(reddish brown), [Fe (SCN)] 2+(blood red), liquid Brtwo(dark reddish brown), BrtwoWater (orange), Brtwo（CClfour）Reddish brown, BrtwoSteam (reddish brown), NOtwo(reddish brown) yellow: Agl (yellow), AgthreePOfour(yellow), S (light yellow), NatwoOtwo(light yellow), AgBr (light yellow), FeClthree(brown yellow), ItwoWater (brown yellow), Fe3+(brown yellow), Cltwo(yellow green) Blue: CuSOfour·5HtwoO、Cu(OH)two、Cu2+Solution green: FeSOfour·7HtwoO、Fe
Second, remember some industrial reactions, such asChlor alkali industry, sulfuric acid industry, etc
Third, remember some special reaction conditions, such as electrolysis, and think that it may be electrolysis of saturated sodium chloride or electrolysis of molten aluminum oxide;high temperatureAccording to whether the reaction isSimple substanceParticipate or generate, and determine whether metal participates or notThermite reaction, iron andWater vaporReactions, etc., as well as some continuous oxidation problems such as HtwoO-SOtwo-SOthree-HtwoSOfour，NHthree-NO-NOtwo-HNOthree
Effect of activity
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The reactivity of the same substance in different structural states varies greatly.
The more complete the structure of reactants is, the fewer character defects are, which is not conducive to diffusion, and the solid phase reaction speed is slow.Strong bonding force between particles, firm structure, high character and low reactivity.
The process of polycrystalline transformation is often accompanied by lattice rearrangement, which makes the lattice loose and activated.E.g. SiOtwoPolycrystalline transformation can make the lattice loose and activated, and easy to break.
Thermal decomposition and dehydration: because gas and steam are discharged from the crystal, the lattice has a large specific surface area and lattice defects, or becomes amorphous after decomposition and dehydration, which increases the reaction activity and accelerates the solid phase reaction.For example, light burned raw materials have much higher reaction activity than dead burned raw materials, CaCOthreeDecompose under light burning to obtain loose and porous CaO, which is beneficial to the combination of CaO and SiOtwoReaction, generating CtwoS。Kaolinite AltwoOthree·2SiOtwo·2HtwoO heating and dehydration to obtain metakaolinite AltwoOthree·2SiOtwo, continue heating to obtain Al with certain activitytwoOthreeAnd SiOtwo。[1]
