When chemical processes occur, energy (typically in the form of heat) is either

Question

When chemical processes occur, energy (typically in the form of heat) is either released-an exothermic process, or absorbed-an endothermic process. The breaking of bounds requires energy to pull the atoms apart; bond-breaking is thus an endothermic process. When bonds are formed, energy is released-precisely the same amount of energy which would be required to break those bonds. Thus, the making of bonds is an exothermic process. In most chemical reactions, bonds are both broken and made. Whether the overall reaction is endothermic or exothermic depends on the energy required to perform the needed changes in bonding. The quantity of energy released or absorbed in a chemical process can be designated by an enthalpy (energy) changes, delta H, for that process. If there is a release of energy when the reaction occurs, the value of delta H is negative, and the reaction is exothermic. If the reaction results in a net consumption of energy, then delta H is positive, and the reaction is endothermic. Critical Thinking Questions Is the chemical reaction in Figure 1 exothermic or endothermic? Is the delta H for the chemical reaction in Figure 1 positive or negative? Provide a chemical reaction with a value of delta H that has the same magnitude of delta H as the reaction in Figure 1, but has the opposite sign. Predict whether each of the following reactions would be exothermic or endothermic: CO(g) rightarrow C(g) + O(g) 2H(g) + O(g) rightarrow H_2O(g) Na^+(g) + Cl^-(g) rightarrow NaCl(s) What is the sign for delat H in each of the reactions in Ex. 1?

Explanation / Answer

5.formation of H2 is exothermic.

6.deltaH would be negative.

7.breaking of hydrogen molecule to H-H will have same magnitude with opposite sign.

1.

a).endothermic

b).exothermic.

C.) endothermic.

2).a-positive

b-negative

c-negative

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