To calculate the total change in bond energy for the reaction \( \text{H}_2 + \text{Cl}_2 \rightarrow 2\text{HCl} \), you first identify the bonds broken and formed. In this reaction, the bonds broken are one H-H bond and one Cl-Cl bond, while the bonds formed are two H-Cl bonds. You would then look up the bond energies for each of these bonds, sum the energies of the bonds broken, and subtract the sum of the energies of the bonds formed from that total. If the result is a positive value, it indicates that more energy was required to break the bonds in the reactants than was released when the products' bonds were formed, making the reaction endothermic. If the result is negative, the reaction is exothermic, meaning that more energy was released than consumed.
Explain how you would calculate the total change in bond energy for the reaction H
2
+Cl
2
→2HCl. How would you know if the reaction was endothermic or exothermic? State your answer in 3-5 sentences.
To calculate the total change in bond energy for this reaction, you need to sum the bond energies of the bonds broken in the reactants and compare them to the sum of the bond energies of the bonds formed in the products. For the reaction, the H-H and Cl-Cl bonds are broken, and two H-Cl bonds are formed. The change in bond energy is calculated by subtracting the total energy of bonds formed from the total energy of bonds broken. If the bond energies of the products are greater than those of the reactants, the reaction is exothermic, releasing energy. Conversely, if the bond energies of the reactants are greater than those of the products, the reaction is endothermic, requiring energy input.
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