Question

2. (5 Pts) Use the table of bond ehthalpies found in your textbook to calculate AH for the following reaction: (You must balance the equation and show the bonding structures and calculations to receive credit.) H200) CO2(g)+ 3. (4 Pts) Draw all the resonance structures that follow the octet rule for SO? and show the formal charges on each atom.

Answer 1

Before going to the calculation part let's 1st balance the chemical reaction.

the balanced chemical reaction will be in the form

C₄H₈ +6 O₂ → 4 CO₂ + 4H₂O

2 2 印H

Now standard bond enthalpies of given molecules are

Bond breaking

C4H8

1 mol C=C = 602 KJ

2 mol C–C = 2 × 346 = 692 KJ

8 mol C–H = 8 × 414 = 3312 KJ

Total energy by breaking of bonds in C4H8 =4406 KJ

O2

6 mol O=O = 6 × 497 = 2982 KJ

TOTAL ENERGY RELEASED AFTER BREAKING OF ALL BONDS IN C4H8 AND O2

=4406 KJ + 2982 KJ =7388 KJ

Total energy put in = + 7388 KJ

Bond making

Energy required to make four Carbon dioxide molecule

=12 mol C=O =12 × 798 = 9576 KJ (One carbon dioxide molecule containing 2 C=O BONDS)

8 mol H–O = 8 × 458 = 3664 KJ(As one molecule of H2O contain two   H–O bonds)

Now Total energy given to make the bonds equal to= 9576 KJ + 3664 KJ = 13240 KJ

Enthalpy of reaction equal to Bond enthalpy of reactants - Bond enthalpy of product

∆H = 7388 KJ -13240 KJ = -5852 KJ/mol

B)

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