Question

use the molar bond enthalpy data in the table to estimate the value of δ∘rxnδhrxn° for the equation c2h4(g) hbr(g)⟶c2h5br(g) c2h4(g) hbr(g)⟶c2h5br(g) the bonding in the molecules is shown.

Answer 1

To estimate ΔH°rxn for the given reaction , calculate the bonds broken and formed in the reaction and subtract their bond dissociation energies. With the given bond dissociation energies, the estimated value of ΔH°rxn is 116 kcal/mol.

Step-by-step explanation:

To estimate the value of ΔH°rxn for the equation C2H4(g) + HBr(g) ⟶ C2H5Br(g), you need to consider the bond dissociation energies of the bonds being broken and formed. In this case, the reactant C2H4(g) has one C-C bond and four C-H bonds, and the product C2H5Br(g) has one C-Br bond and three C-H bonds. Refer to Table 7.2.1 for the bond dissociation energies:

C-C bond: 83 kcal/mol

C-H bond: 100 kcal/mol

C-Br bond: 67 kcal/mol

Using the formula for enthalpy change, ΔH°rxn = (bonds broken) - (bonds formed), the calculation would be:

ΔH°rxn = [(1 C-C bond x 83 kcal/mol) + (4 C-H bonds x 100 kcal/mol)] - [(1 C-Br bond x 67 kcal/mol) + (3 C-H bonds x 100 kcal/mol)]

ΔH°rxn = (83 + 400) - (67 + 300) = 116 kcal/mol

Answer 2

To estimate the value of the standard enthalpy change (ΔH°) for the given reaction, we need to calculate the total bond dissociation energy for the reactants and the products.

Step-by-step explanation:

To estimate the value of the standard enthalpy change (ΔH°) for the given reaction, we need to calculate the total bond dissociation energy for the reactants and the products. In this case, the reactants are C2H4 and HBr, and the product is C2H5Br.

The bond dissociation energies for the reactants are: C-C (347 kJ/mol), C-H (413 kJ/mol), and H-Br (366 kJ/mol). The bond dissociation energy for the product C2H5-Br is 280 kJ/mol.

To calculate the enthalpy change (ΔH°) for the reaction, we subtract the sum of the bond dissociation energies of the bonds broken in the reactants from the sum of the bond dissociation energies of the bonds formed in the products. In this case, it would be:

(2 x C-C) + (4 x C-H) + (2 x H-Br) - (1 x C2H5-Br)