The dissociation of water into H 3 O + and OH – ions depends on temperature. At 0 °C the [H 3 O + ] = 3.38 x 10 –8 M , at 25 °C the [H 3 O + ] = 1.00 x 10 –7 M , and at 50 °C the [H 3 O + ] = 2.34 x 10 –7 M . c. Is the dissociation of water endothermic or exothermic?

Hey, everyone, we're told that the temperature affects the dissociation of water into hydro ni um and hydroxide ions at five degrees Celsius, the concentration of hydrogen ions is equal to 4.32 times 10 to the negative eight mol per kilogram of water. At 25 degrees Celsius, the concentration of hydrogen ions is equal to 1.0 times 10 to the negative seven mol per kilogram of water. And at 45 degrees Celsius, the concentration of hydro ni um ions is equal to 1.97 times 10 to the negative seven mol per kilogram of water. Determine if the dissociation of water into hydro knee. Um and hydroxide ions is endo thermic or eggs. A thermic 1st. Let's go ahead and recall the dissociation reaction of water and that's going to be two of our water. And this will dissociate into our hydro ni um ions plus our hydroxide ions and our waters are reacted while our hydro ni um ion and a hydroxide ions are the products. Now, let's go ahead and compare our temperatures. So at five degrees Celsius, we see that the concentration of our hydro ni um ions is 4. times 10 to the negative eight mol per kilogram. Now looking at 25 degrees Celsius, we see that this value becomes 1.0 times 10 to the negative seven mol per kilogram. Now at 45 degrees Celsius, we see that this becomes 1.97 times 10 to the negative seven mol per kilogram. Now looking at this trend, we can see that the concentration of our hydro ni um ions increases as our temperature increases. So the increase in the concentration of hydrogen ions due to the temperature increase means that the formation of the products is favorable. So when the addition of heat shifts the equilibrium forward or to the right, which is our product side and the ratio of the products to reactant will increase consequently. So this means that the process is going to be endo thermic which is going to be our final answer. Now, I hope this made sense and let us know if you have any questions.

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Problem 99c

Textbook Question

The dissociation of water into H₃O⁺ and OH^– ions depends on temperature. At 0 °C the [H₃O⁺] = 3.38 x 10^–8 M, at 25 °C the [H₃O⁺] = 1.00 x 10^–7 M, and at 50 °C the [H₃O⁺] = 2.34 x 10^–7 M.
c. Is the dissociation of water endothermic or exothermic?

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Step 1: Understand the relationship between temperature and the dissociation of water. The dissociation of water into H₃O⁺ and OH⁻ ions is influenced by temperature, and the equilibrium constant (Kw) increases as temperature increases.

Step 2: Recall the principle of Le Chatelier's Principle. If a reaction is endothermic, increasing temperature will favor the forward reaction (more dissociation). If a reaction is exothermic, increasing temperature will favor the reverse reaction (less dissociation).

Step 3: Analyze the data provided. At higher temperatures (25 °C and 50 °C), the concentration of H₃O⁺ increases compared to lower temperatures (0 °C). This indicates that the dissociation of water is favored as temperature increases.

Step 4: Connect the observation to thermodynamics. Since the dissociation of water is favored at higher temperatures, this suggests that the process absorbs heat, which is characteristic of an endothermic reaction.

Step 5: Conclude that the dissociation of water is endothermic based on the increase in [H₃O⁺] with temperature, consistent with the absorption of heat during the dissociation process.

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Key Concepts

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

Dissociation of Water

The dissociation of water refers to the process where water (H₂O) breaks down into hydronium (H₃O⁺) and hydroxide (OH⁻) ions. This equilibrium is influenced by temperature, as changes in temperature can shift the concentrations of these ions in solution. Understanding this process is crucial for analyzing how temperature affects the acidity and basicity of water.

Endothermic vs. Exothermic Reactions

Endothermic reactions absorb heat from their surroundings, leading to a decrease in temperature, while exothermic reactions release heat, resulting in an increase in temperature. The classification of a reaction as endothermic or exothermic can be determined by observing temperature changes during the reaction. This concept is essential for understanding the thermal dynamics of the dissociation of water.

Temperature Dependence of Equilibrium

The temperature dependence of equilibrium states that the position of equilibrium in a chemical reaction can shift with changes in temperature, as described by Le Chatelier's principle. For the dissociation of water, an increase in temperature typically favors the formation of products (H₃O⁺ and OH⁻), indicating that the reaction is endothermic. This principle helps in predicting how temperature variations affect the dissociation process.

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