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Ch.16 - Aqueous Equilibria: Acids & Bases
McMurry - Chemistry 8th Edition
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Tutti i libri di testoMcMurry 8th EditionCh.16 - Aqueous Equilibria: Acids & BasesProblema 73
Capitolo 16, Problema 73

Water at 500 °C and 250 atm is a supercritical fluid. Under these conditions, Kw is approximately 1.7 * 10^-19. Estimate [H3O+] and [OH-] at 500 °C. Is the water acidic, basic, or neutral?

Guida verificata passo dopo passo
1
Step 1: Understand the concept of the ion product of water (Kw). Kw is the equilibrium constant for the self-ionization of water, given by the expression Kw = [H3O+][OH-]. At 25 °C, Kw is 1.0 x 10^-14, but it changes with temperature.
Step 2: Recognize that at 500 °C, Kw is given as 1.7 x 10^-19. This means that the product of the concentrations of hydronium ions [H3O+] and hydroxide ions [OH-] is 1.7 x 10^-19.
Step 3: Assume that the concentrations of [H3O+] and [OH-] are equal in pure water, as water is neutral. Let [H3O+] = [OH-] = x.
Step 4: Substitute x for both [H3O+] and [OH-] in the expression for Kw: (x)(x) = 1.7 x 10^-19. This simplifies to x^2 = 1.7 x 10^-19.
Step 5: Solve for x by taking the square root of both sides to find the concentration of [H3O+] and [OH-]. Compare the concentrations to determine if the water is acidic, basic, or neutral.

Concetti chiave

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Supercritical Fluids

Supercritical fluids occur when a substance is above its critical temperature and pressure, leading to unique properties that differ from those of gases and liquids. In this state, the fluid can diffuse through solids like a gas and dissolve materials like a liquid, which is significant in understanding the behavior of water at high temperatures and pressures.
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States of Matter of Phase Diagrams

Ion Product of Water (Kw)

Kw, the ion product of water, is the equilibrium constant for the self-ionization of water, represented as Kw = [H3O+][OH-]. At different temperatures, Kw varies; at 25 °C, it is 1.0 x 10^-14, but at 500 °C, it increases to approximately 1.7 x 10^-19, indicating a higher concentration of ions in supercritical water, which affects its acidity or basicity.
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Production of Hydrogen Example

Acidity and Basicity

The acidity or basicity of a solution is determined by the concentrations of hydronium ions [H3O+] and hydroxide ions [OH-]. A neutral solution has equal concentrations of both ions, while an acidic solution has a higher concentration of [H3O+], and a basic solution has a higher concentration of [OH-]. By calculating [H3O+] and [OH-] from Kw, one can determine the nature of the water at 500 °C.
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Anion Acidity and Basicity
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