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To determine whether H+ ions in HCl act as a catalyst in the reaction between hydrochloric acid and sodium thiosulfate. Chemistry was an HL subject for me.Descripción completa
To determine whether H+ ions in HCl act as a catalyst in the reaction between hydrochloric acid and sodium thiosulfate. Chemistry was an HL subject for me.
CBSE Class-12 Chemistry Quick Revision Notes Chapter-04: Chemical inetics
•
Chemical kinetics: It is the branch of chemistry that deals with the study of reaction rates and their mechanisms.
•
Rate of reaction: It is the change in concentration of reactant (or product) in unit time.
•
The unit of rate of reaction is mol L!s!. "#$%C#& − d [ A] Rate of disappearance of A = dt
•
where d'" is small change in conc. of "* and dt is small inter+al of time −d [ B ] Rate of disappearance of B = dt ,here d'$ is small change in conc. of $* and dt is small inter+al of time + d [C ] Rate of appearance of C = dt ,here d'C is small change in conc. of C* and dt is small inter+al of time +d[ D] Rate of appearance of D = dt ,here d'& is small change in conc. of &* and dt is small inter+al of time
Rate
=
− d [ A]
dt
=
−d [ B ]
dt
=
+d [C ]
dt
=
+ d [D ]
dt
•
Rate law or rate e-uation: It is the epression which relates the rate of reaction with concentration of the reactants. The constant of proportionality k* is known as rate constant.
•
"+erage rate: It is the rate of reaction measured o+er a long time inter+al. ∆ x "+erage rate = ∆t where is / change in concentration and /t is large inter+al of time.
•
Instantaneous rate: It is the rate of reaction when the a+erage rate is taken o+er a particular moment of time. dx Instantaneous rate = . dt where d is small change in i n conc. and dt is the smallest inter+al of time.
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It is the epression which relates the rate of reaction with concentration of the reactants. •
•
Rate constant: ,hen the concentration of reactants is unity0 then the rate of reaction is known as rate constant. It is also called specific reaction rate. The constant of proportionality k* is known as rate constant.
•
1olecularity of a reaction: The total number of atoms0 ions or molecules of the reactants in+ol+ed in the reaction is termed as its molecularity. It is always in whole number and is ne+er more than three. It cannot be 2ero.
•
3rder of a reaction: The sum of the eponents (power) of the concentration of reactants in the rate law is termed as order of the reaction. It can be in fraction. It can be 2ero also.
•
If rate law epression for a reaction is Rate 4 k '" '$y Then its order of reaction 4 # y 3rder cannot be determined with a gi+en balanced chemical e-uation. It can be eperimentally determined.
•
•
Integrated rate law for 2ero order reaction: R%5 dx 0 = k[ R] dt [ R ] − [ R ] k = 0 t
•
If we plot a graph between concentration of R +s time t0 the graph is a straight line with slope e-ual to k and intercept is e-ual to 'Ro. 6alf life of a reaction: The time taken for a reaction0 when half of the starting material has reacted is called half life of a reaction.
•
•
7or 2ero order reaction0 the halflife time is [ R ] t 1/2 = 0 2k
•
7or first order reaction0 the halflife time is 0.693 t 1/2 = k where k* is rate constant It is independent of initial concentration for first order reaction.
•
Rate law for first order reaction: R5 [ R ] 2.303 log 0 k = [ R] t
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where k* is rate constant or specific reaction rate0 'Ro is initial molar conc.0 'R is final molar conc. after time t*. 2.303 a log k = t a−x where a* is initial conc. reacted in time t* final conc.0 after time t* is (a 8 ). •
If we plot a graph between ln'R with time0 we get a straight line whose slope 4 k and intercept ln'Ro.
•
To calculate rate constant for first order gas phase reaction of the type " (g) $(g) # C(g) 2.303 p1 log k = (2 pi − pt ) t ,here pi is initial pressure of "0 pt is total pressure of gaseous miture containing " 0 $0 C p t 4 p " # p $ # p C
•
5seudo first order reaction: The reaction which is bimolecular but order is one is called pseudo first order reaction. This happens when one of the reactants is in large ecess. 9ample "cidic hydrolysis of ester (ethyl acetate). +
H
CH 3COOC2 H 5 + H 2O → CH 3COOH
+ C 2 H 5OH
•
"cti+ation energy (9a): It is etra energy which must be possessed by reactant molecules so that collision between reactant molecules is effecti+e and leads to the formation of product molecules.
•
"rrhenius e-uation of reaction rate: It gi+es the relation between rate of reaction and temperature. k
=
ln k
Ae =
log k
− Ea / RT
ln A − Ea / RT
=
log A −
E a
2.303 RT where k 4 rate constant0 " 4 fre-uency factor0 9a 4 energy of acti+ation R 4 gas constant0 T 4 temperature in el+in0
log •
k2 k1
=
T2 − T 1 2.303R T1T2 E a
5robability factor or ;teric factor − E a
Rate = PZ AB .e RT − E a
,here <"$ represents the collision fre-uency of reactants0 " and $0 e RT represents the fraction of molecules with energies e-ual to or greater than 9a and 5 is called the probability or steric factor. •
1echanism of reaction:
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It is the se-uence of elementary processes leading to the o+erall stoichiometry of a chemical reaction. •
"cti+ated comple: It is an unstable intermediate formed between reacting molecules. ;ince0 it is highly unstable and it readily changes into product.
•
Rate determining step: It is the slowest step in the reaction mechanism. The number of collisions per second per unit +olume of the reaction miture is known as collision fre-uency (<).
•
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