Chemical kinetics

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طبعا عارفين ان أى chemical reaction فى الدنيا له rate

و الـ rate بيكون عبارة عن : change in conc. Of the reactants (or product) in certain time.

aA + bB <---> cC + dD

so, Rate= change in conc. In mole\ change in time

= dx\dt (differential not delta)

= ^ [ pdt]\^t = - ^ [reactant]\^t ( ^ delta)

Types of Rn. Rate :

1 – Average Rate : rate () 2 diff. times

And det. From ! slope.

2 – Instantaneous Rate : rate @ certain time.

( @ ! certain point draw ! tangent, then calc. ! rate)

3 – Initial Rate: rate @ time = 0.

4 reactants only ( as there is no pdts)

*N.B:

- Molecularity: no. of molecules participate n ! Rn. , there are 3 types :

1 – Unimolecular : H2O2--> H2O + ½ O2

2 – Bimolecular : CO + NO2--> CO2 + NO

2O3 --> 3O2

3 – Termolecular : 2NO2 + F2 --> 2NO2F

3C2H2 -->C6H6

- Rn. Mech. : usually include multi steps, 1 of them is very slow & called “ Rate det. Step”

- Order of Rn. : molecularity of rate det. Step.

It depends on ! Rn. Mech. & det. Only by experiment.

It is ! sum of ! orders of ! reactants.

- R= K[A]~a[B]~b

Where K= rate const.

Rate const. only depends on temp.

While rate of ! Rn. Depends on :

1 – Nature of ! reactants. (no. of molecules , ph. State, ….)

2 – conc. Of ! reactants . ( as ! conc. ^ ,! Rn. Rate ^)

3 – Temp. (as ^ , R ^)

4 – Order. ( ctrl how ! reactant conc. Affact ! rate)

5 – catalyst .( ^ R)

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