9. A hypothetical reaction is shown below, in which A, B, C, and D are all coval

Question

9. A hypothetical reaction is shown below, in which A, B, C, and D are all covalent compounds. The number under each "compound" is the standard enthalpy of formation of that substance, per mole of substance. Ho (kJ/mol) +15.7 -86.4 -52.7 +71.6 a) Use the provided AHa values to calculate the enthalpy change (AHr) for the reaction shown. (12 points) b) Is this reaction exothermic or endothermic? How do you know? (5 points) c) Are the reactants or the products likely to have the strongest bonds? How do you know? (5 points) 3-4

Explanation / Answer

Ans :

a) The enthalpy change of the reaction is the difference between the enthalpy of products and reactants.

So here , the enthalpy change is given as:

= 7(71.6) + 4(-52.7) - 3(15.7) - 4(-86.4)

= 588.9 KJ

b) Since the enthalpy change for the reaction has positive value , the reaction is endothermic , which means that the heat has been absorbed.

c) The energy is required to break the bonds and energy is released when new bonds are formed. Here the change in enthalpy is positive , which means that the products have strongest bonds.

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