ThermochemistryMedium
Question
The standard enthalpy combustion at 25oC of hydrogen, cyclohexene (C6H10) and cyclohexane (C6H12) are - 241, - 3800 and - 3920 kj/ mole respectively. Calculate the heat of hydrogenation of cyclothexene.
Options
A.- 111kJ/mole
B.- 121kJ/mole
C.- 118kJ/mole
D.- 128 kJ/mole
Solution
The required reaction is
C6H10 + H12 → C6H12, ᐃH1 = ? .....(i)
Cyclohexeme Cyclohexame
Let us write the give facts
H2 +
O2 → H2O;
ᐃH2 = - 241 kJ/mole .....(ii)
C6H10 +
O2 → 6CO2 + 5H2O
H3 = - 3800kJ/mole .....(iii)
C6H12 + 9O2 → 6CO2 + 6H2O
H4 = - 3920kJ/mole ..........(4)
The required reaction rectional (1)Can be obained by adding equations (2) and (3) andsubracting (4) From the sum of (2) and (3).
C6H10 + H29O2 → C6H12
ᐃH1 = (ᐃH2 = ᐃH3) - ᐃH4
= [-241+ (-3800)] - (-3920)
=(-241 - 3800) - (- 3920)
= -4041 + 3920 = - 121kJ/mole
C6H10 + H12
Cyclohexeme Cyclohexame
Let us write the give facts
H2 +
O2 ᐃH2 = - 241 kJ/mole .....(ii)
C6H10 +
O2 H3 = - 3800kJ/mole .....(iii)
C6H12 + 9O2
H4 = - 3920kJ/mole ..........(4)
The required reaction rectional (1)Can be obained by adding equations (2) and (3) andsubracting (4) From the sum of (2) and (3).
C6H10 + H29O2
ᐃH1 = (ᐃH2 = ᐃH3) - ᐃH4
= [-241+ (-3800)] - (-3920)
=(-241 - 3800) - (- 3920)
= -4041 + 3920 = - 121kJ/mole
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