Answer:
c)
Explanation:
The reaction between ethene and HBr is:
CH2=CH2 + HBr → CH3CH2Br
Thus, the double bond C=C and the bond H-Br were broken, and the bonds C-C, C-H and C-Br were formed. The enthalpy of the reaction (the energy change), is the sum of the enthalpies of the reactions that were broken with the bonds that were created.
To break a bond, it's necessary to the molecule to gain energy, thus the process is endothermic and H>0, and to form a bond, it's necessary to release energy, and so H<0, so:
ΔH = ∑n*Hbroken - ∑n*Hformed, where n is the coefficient of the substance, so:
ΔH = (612 + 366) - (348+412+276)
ΔH = -58 kJ/mol
The minus signal indicates that the energy was released.
