Consider a hypothetical chemical reaction: A + B ? C + D (In...

Consider a hypothetical chemical reaction: A + B ? C + D (In this equation A, B, C and D stand for some unknown chemical formulas.) Here is an energy diagram for the reaction: 400 300 energy A + B 200 (kJ/mol) C + D 100 0 reaction coordinate Use the energy diagram to answer these questions. What is the heat of reaction? kJ/mol Exothermic Is the reaction exothermic or endothermic? Endothermic Neither Yes, it's kJ/mol Can you determine the activation energy? No. Can you determine the activation energy of the reverse reaction? Yes, it's kJ/mol C + D ? A + B No.

Transcript

00:01 Hi, we are given an energy diagram for the reaction a plus b gives c plus d.

00:07 An energy diagram shows the energy of reactants and the products and the change in the energy during the reaction.

00:16 Now in this energy diagram a and b are the reactants at the energy level 200 kilojoules per mole and the products are c and d with energy of 150 kilojoules per mole.

00:30 Now for part a we need to calculate the heat of reaction.

00:34 The heat of reaction is the difference in the energy of the products and the energy of the reactants.

00:44 So this is calculated as energy of products minus energy of reactants.

00:49 Now in this graph we can see that energy of reactants is 200 kilojoules per mole and the energy of products is 150 kilojoules.

01:01 Per mole.

01:02 So the heat of reaction comes out to be minus 50 kilojoules per mole.

01:07 Now as the heat is released, minus signs suggest that there is a release of heat.

01:13 Now as there is release of heat during this reaction, it is an exothermic reaction.

01:20 Also whenever, when the products are at lower energy than the reactants, then it is an exothermic reaction.

01:28 And if products are at higher energy as compared to reactants, then it is an endothermic reaction.

01:34 Now for c part, we need to know what is an activation energy.

01:39 Activation, this is the transition state, this point...

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