Engineering Chemistry S Datta

108 ENGINEERING CHEMISTRY
Examples of a First Order Reaction
(i) Decomposition (gas phase)
(a) 2N 2
O 5
⎯⎯→ 4NO 2
+ O 2
(b) N 2
O 4
⎯⎯→ 2NO 2
(c) CH 3
CH 2
Cl ⎯⎯→ C 2
H 4
+ Cl 2
CH2
⎯ CH2
(d) ⏐ ⏐ ⎯⎯→ 2C 2
H 4
CH2
⎯ CH2
ethylene
cyclobutane
(ii) Isomerisation (gas phase)
(a) CH2 CH 2 CH3CH = CH2
propylene
CH 2
cyclopropane
(b) CH⎯
CH ⎯⎯→ CH
2
2
= CH—CHe = CH 2
⏐ ⏐
1, 3-butadien.
CH⎯
CH2
Cyclobutene
(iii) Decomposition (solution phase)
(a) H 2
O 2
⎯⎯→ H 2
O + 1 2 O 2
COOH
ON 2 NO 2
ON 2
NO 2
(b)
NO 2 NO 2
(iv) Hydrolysis
C 12
H 22
O 11
+ H 2
O ⎯⎯→ C 6
H 12
O 6
+ C 6
H 12
O 6
Cane Sugar Glucose Fructose
(v) Solvolysis
(CH 3
CO) 2
O + 2C 2
H 5
OH ⎯⎯→ 2 CH 3
COOC 2
H 5
+ H 2
O
(vi) Radioactive disintegration:
Ra ⎯⎯→ Rn + α
Mathematical Formulation of a Second Order Reaction
Reactions in which two molecules, identical or different, take part and the rate of the
reaction is proportional to the concentration of each of them, are called second order reaction.
Let, the reaction be represented by,
A + B ⎯⎯→ C + D
Initial concentration of A = a
Initial concentration of B = b