1)

Using the data provided, calculate the multiple bond energy (kJ mol-1)of a CC bond C2H2. That energy is (take the bond energy of a C-H bond as 350k Jmol-1)

2C(s)+H2(g)C2H2(g);     H=225kJmol1

2C(s)2C(g)      H=1410kJmol1

H2(g)2H(g)   H=330kJMol1


A) 450 k J/mol

B) 755 k J/mol

C) 380 k J/mol

D) 815 k J/mol

Answer:

Option D

Explanation:

For the calaculation of CC  bond energy we must first calculate dissociation energy of C2H2 as

 C2H2(g) 2C(g)+2H(g).....(i)

 Using the given bond energoes and enthalpies

 C2H2(g)2C(g)+2H(g);

                             H=225kJ ........(ii)

2C(s)2C(g); H=1410kJ..........(iii)

 H2(g)2H(g); H=330kJ......(iv)

 adding equation (ii),(iii) and (iv) gives equation(i)

       C2H2(g)2C(g)+2H(g);

                                       H=1515kJ

      1515kJ=2× (C-H)BE+(CC)BE

 =2×350+(CC)BE

     (CC)BE=1515-700=815 kJ/mol