Oxygen can be converted into ozone by the action of lightning or electric sparks: 3 O 2 (g) ⇌ 2 O 3 (g) For this reaction, ∆ H = +69kcal/mol (+285 kj/mol) and K = 2.68 × 10 -29 at 25 °C. a. Is the reaction exothermic or endothermic?

Hello. In this problem, we're told at 25 degrees Celsius, the change in entropy and the equilibrium constant for the conversion of di nitrogen tetroxide to nitrogen dioxide are 13.68 kilocalories per mole or 57.24 killed drills per mole and 0. respectfully grasses the reaction endo thermic or Xr thermic To determine whether the reaction is exo thermic or endo thermic, we look at the change in entropy which is equal to a positive 13.68 hill calories per mole. Since our change in entropy, the reaction is positive. In sign, it tells that the, this is a endo thermic reaction. Looking at a reaction profile diagram where we have energy on the y axis is a function of the reaction. Progress on the x axis. We begin with the energy of our reactant and end with the energy of our products. The difference between the energy of our products and that of our reactions is equal to the empathy of reaction. If our products are higher engine you than our reactant, then that tells us that the system you need energy. And so the change in entropy for the reaction should be positive in sign. So the answer is that the reaction in this case is endo thermic. So we have a positive change in the entropy for the reaction. Thanks for watching, hope this helped.

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7. Energy, Rate and Equilibrium

Endothermic & Exothermic Reactions

GOB Chemistry

7. Energy, Rate and Equilibrium

Endothermic & Exothermic Reactions

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1:46 minutes

Problem 59a

Textbook Question

Oxygen can be converted into ozone by the action of lightning or electric sparks:
3 O₂(g) ⇌ 2 O₃(g)
For this reaction, ∆H = +69kcal/mol (+285 kj/mol) and K = 2.68 × 10^-29 at 25 °C.
a. Is the reaction exothermic or endothermic?

Verified step by step guidance

Identify whether the reaction absorbs or releases heat by analyzing the given enthalpy change (∆H). A positive ∆H value indicates that the reaction absorbs heat, making it endothermic, while a negative ∆H value would indicate an exothermic reaction.

In this problem, the enthalpy change (∆H) is given as +69 kcal/mol (+285 kJ/mol). Since the value is positive, this means the reaction absorbs heat from the surroundings.

Conclude that the reaction is endothermic because it requires energy input to proceed, as indicated by the positive ∆H value.

Recall that endothermic reactions are typically associated with an increase in the energy of the system, as energy is absorbed to form the products.

Note that the equilibrium constant (K) being very small (2.68 x 10^-29) at 25 °C suggests that the reaction strongly favors the reactants (O2) under standard conditions, but this does not affect the classification of the reaction as endothermic.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Endothermic and Exothermic Reactions

Endothermic reactions absorb heat from their surroundings, resulting in a positive change in enthalpy (∆H > 0). Conversely, exothermic reactions release heat, leading to a negative change in enthalpy (∆H < 0). In this case, since the reaction has a positive ∆H of +69 kcal/mol, it indicates that the reaction is endothermic.

Enthalpy Change (∆H)

Enthalpy change (∆H) is a measure of the heat content of a system at constant pressure. It indicates whether a reaction absorbs or releases energy. A positive ∆H value signifies that energy is absorbed during the reaction, while a negative value indicates energy release. For the given reaction, the positive ∆H confirms it is endothermic.

Equilibrium Constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a reversible reaction. A very small K value, such as 2.68 x 10^-29, suggests that at equilibrium, the reactants are favored over the products, indicating that the formation of ozone (O3) from oxygen (O2) is not favored under standard conditions.