Question

The \(\mathrm{pH}\) of a solution of \(\mathrm{H}_{2} \mathrm{O}_{2}\) is \(6.0 .\) Some chlorine gas is bubbled into this solution. Which of the following is correct? (a) The \(\mathrm{pH}\) of resultant solution becomes \(8.0\) (b) Hydrogen gas is liberated from resultant solution (c) The \(\mathrm{pH}\) of resultant solution becomes less than \(6.0\) oxygen gas is liberated (d) \(\mathrm{Cl}_{2} \mathrm{O}\) is formed in the resultant solution

Short answer

(c) The pH of the resultant solution becomes less than 6.0, oxygen gas is liberated.

Step-by-step solution

Understanding the Problem

We have a solution of \(\mathrm{H}_2\mathrm{O}_2\) with a \(\mathrm{pH}\) of 6.0. Chlorine gas \((\mathrm{Cl}_2)\) will be bubbled into this solution. We need to predict what happens to the \(\mathrm{pH}\) and other chemical reactions after this addition from the given options.

Examining the Behavior of \(\mathrm{H}_2\mathrm{O}_2\) with Acidic and Basic Solutions

\(\mathrm{H}_2\mathrm{O}_2\) can function as both an oxidizing and reducing agent. The initial \(\mathrm{pH}\) of 6.0 indicates a near-neutral solution, hinting that \(\mathrm{H}_2\mathrm{O}_2\) can slightly ionize to form \(\mathrm{H}^+\). Chlorine gas addition alters this equilibrium.

Reaction of \(\mathrm{Cl}_2\) with \(\mathrm{H}_2\mathrm{O}_2\)

Chlorine gas is known to form hypochlorous acid and hydrochloric acid upon reacting with water: \[ \mathrm{Cl}_2 + \mathrm{H}_2O \rightarrow \mathrm{HCl} + \mathrm{HOCl} \]Both products (\(\mathrm{HCl}\) and \(\mathrm{HOCl}\)) are acidic.

Effects of the Reaction on \(\mathrm{pH}\)

The addition of \(\mathrm{HCl}\) and \(\mathrm{HOCl}\) will increase the concentration of \(\mathrm{H}^+\) ions, making the resultant solution more acidic. Therefore, the \(\mathrm{pH}\) will decrease from 6.0 to a value lower than 6.0.

Identification of Other Products

The oxidation of \(\mathrm{H}_2\mathrm{O}_2\) or other complex reactions in the presence of \(\mathrm{Cl}_2\) could lead to oxygen gas being released. This would occur as \(\mathrm{H}_2\mathrm{O}_2\) decomposes, typically forming \(\mathrm{O}_2\) gas.

Key concepts

Hydrogen Peroxide Behavior

Hydrogen peroxide, or \(\mathrm{H}_2\mathrm{O}_2\), is a fascinating chemical due to its dual ability to act as both an oxidizing and reducing agent. In more basic terms, this means it can either gain or lose electrons during reactions. This versatility plays a significant role in its interactions with other compounds.
In water, hydrogen peroxide slightly ionizes which results in the formation of \(\mathrm{H}^+\) ions. This behavior is crucial when discussing pH, as these ions suggest it can create a mildly acidic environment. The initial pH of \(6.0\) for the \(\mathrm{H}_2\mathrm{O}_2\) solution indicates a near-neutral terrain, which shows the delicate state of equilibrium in hydrogen peroxide solutions. Thus, any additions, like chlorine gas, can easily tip this balance.
When dealing with reactions, one must consider how the inherent properties of \(\mathrm{H}_2\mathrm{O}_2\) might affect the resulting solution. This sensitivity makes the compound a center of many significant chemical discussions.

Chlorine Gas Reactions

Chlorine gas, \(\mathrm{Cl}_2\), is well-known for its reactive nature, particularly in aqueous environments. When \(\mathrm{Cl}_2\) is introduced into water, it forms hypochlorous acid (\(\mathrm{HOCl}\)) and hydrochloric acid (\(\mathrm{HCl}\)). These reactions can be expressed with the simple equation:

• \(\mathrm{Cl}_2 + \mathrm{H}_2O \rightarrow \mathrm{HCl} + \mathrm{HOCl}\)

This transformation is a result of the dissolution of \(\mathrm{Cl}_2\) where it undergoes hydrolysis, a process that reveals the acidic potential of chlorine gas. The products of this reaction, \(\mathrm{HCl}\) and \(\mathrm{HOCl}\), both contribute \(\mathrm{H}^+\) ions to the solution, emphasizing the shift toward a more acidic environment.
Given these details, the interaction between chlorine gas and water significantly impacts the pH of the solution involved. This mechanism is a vital aspect of understanding the ramifications of bubbling chlorine into an \(\mathrm{H}_2\mathrm{O}_2\) solution.

Reaction Products in Chemistry

The complexity of chemical reactions unveils numerous products, particularly when reactive species like \(\mathrm{H}_2\mathrm{O}_2\) and \(\mathrm{Cl}_2\) interact.
During this reaction, not only do acidic compounds emerge but the oxidation of hydrogen peroxide can lead to the liberation of oxygen gas. As \(\mathrm{H}_2\mathrm{O}_2\) often decomposes in various reactions, oxygen (\(\mathrm{O}_2\)) is likely produced, which may escape as gas bubbles.
This liberation is a common feature in reactions involving peroxides, and it represents an essential aspect of the by-products of these many-step chemical processes. The understanding of how new products like \(\mathrm{HCl}\), \(\mathrm{HOCl}\), and \(\mathrm{O}_2\) come about is integral in estimating the behavior of the resultant solution.

Acid-Base Equilibrium

Acid-base equilibrium describes the balance between acidic and basic ions in a solution. It is a fundamental concept in chemistry, dictating the pH of the solution.
As chlorine gas reacts with water to produce \(\mathrm{HCl}\) and \(\mathrm{HOCl}\), both being acids, the equilibrium shifts to a more acidic stance. Consequently, the addition of these acids increases the concentration of \(\mathrm{H}^+\) ions. This increase lowers the pH of the solution, a direct illustration of deviation in equilibrium.
The initial hydrogen peroxide solution was hovering around pH 6.0, but with the production of more \(\mathrm{H}^+\) and the subsequent overwhelming presence of acidic compounds, a darker shade of acidity should be expected.
In chemical practice, tracking how acids or bases shift the pH of solutions provides insight into reaction outcomes and solution characteristics, which is fundamental for properly predicting and controlling chemical environments.