Write in brief the exssential differences between exothermic and an endothermic

Question

Write in brief the exssential differences between exothermic and an endothermic reactions. Indentify if exothermic endothermic reactions H_2 + I_2 + 12 Kcal rightarrow 2HI CH_4 + 2O_2 rightarrow CO_2 + 213 Kcal Predict which of the following reactions are spontaneous CO_2(S) rightarrow CO_2(g) at 25 degree c CO_2(g) rightarrow C(S) + O_2(g) at 25 degree c Arrange the following sets of anions in order of increasing ionic radii: Br^-, CI^-, I^- Consider the following bonds : N-S. H-H, Na-F, K.-CI, F-CI Rank the bonds in order of increasing polarity Classify each bond as nonpolar covalent, polar covalent or ionic Predict the type of bonding SO_2 Na_2 O PCl_3 Cl_2

Explanation / Answer

1. An exothermic reaction occurs when the temperature of a system increases due to the evolution of heat. This heat is released into the surroundings, resulting in an overall negative quantity for the heat of reaction (qrxn<0qrxn<0). An endothermic reaction occurs when the temperature of an isolated system decreases while the surroundings of a non-isolated system gains heat. Endothermic reactions result in an overall positive heat of reaction (qrxn>0qrxn>0).

System of reactants that absorbs heat from the surroundings in an endothermic reaction has a positive HH, because the enthalpy of the products is higher than the enthalpy of the reactants of the system. Because the enthalpies of these reactions are greater than zero, they are endothermic reactions.

A system that releases heat to the surroundings, an exothermic reaction, has a negative H by convention, because the enthalpy of the products is lower than the enthalpy of the reactants of the system. The enthalpies of these reactions are less than zero, and are therefore exothermic reactions.

2. The best way to know this is with the free energy of gibbs,
G = H – T * S

G<0 = spontanious (negative)
G>0 = non spontaneous (positive

We don't have the numerical values but we do know that monoatomic and diatomic molecules does not contribute to gibbs energy, and in the second reaction, the products do not contribute to that, so the G would be negative, and this reaction would be spontaneous.

The other question post them in another question thread.

Hope this helps

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