Problem 84 - A Complete Resource Book in Chemistry for JEE Main

Question

The oxidation states of the most electronegative element in the products of the reaction, \(\mathrm{BaO}_{2}\) with dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\) are (a) 0 and \(-1\) (b) \(-1\) and \(-2\) (c) \(-2\) and 0 (d) \(-2\) and \(+1\)

Step-by-Step Solution

Answer

Answer: b) \(-1\) and \(-2\).

Step 1: Balance Chemical Reaction

The reaction between barium peroxide \( \mathrm{BaO}_2 \) and dilute sulfuric acid \( \mathrm{H}_{2} \mathrm{SO}_{4} \) can be written as: \( \mathrm{BaO}_2 + \mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{BaSO}_{4} + \mathrm{H}_{2} \mathrm{O}_{2} \). This reaction balances the formation of barium sulfate and hydrogen peroxide as products.

Step 2: Identify Products

The products of this reaction are barium sulfate \( \mathrm{BaSO}_{4} \) and hydrogen peroxide \( \mathrm{H}_{2} \mathrm{O}_{2} \). We will focus on hydrogen peroxide \( \mathrm{H}_{2} \mathrm{O}_{2} \), as it contains the most electronegative element present, which is oxygen.

Step 3: Determine Oxidation States

In \( \mathrm{H}_{2} \mathrm{O}_{2} \), hydrogen typically has an oxidation state of \(+1\). Since the compound is neutral, we balance the charge with oxygen to find its oxidation state. Let the oxidation state of oxygen be \(x\), thus two hydrogen atoms contribute \(+2\), leading to the equation: \( 2x + 2(-1) = 0 \). Solving for \(x\), we get \(x = -1\).

Step 4: Examine Other Product for Oxygen

In \( \mathrm{BaSO}_{4} \), oxygen's typical oxidation state is \(-2\), and it remains as such since barium and sulfur form their usual oxidation numbers of \(+2\) and \(+6\) respectively. Thus, oxygen in \( \mathrm{BaSO}_{4} \) maintains \(-2\).

Step 5: Conclusion on Oxidation States

The oxidation states of the most electronegative element, oxygen, in the products \( \mathrm{H}_{2} \mathrm{O}_{2} \) and \( \mathrm{BaSO}_{4} \), are \(-1\) and \(-2\) respectively. Therefore, the correct answer is \((-1)\) and \((-2)\).

Key Concepts

Barium Peroxide

Barium peroxide, represented chemically as \( \mathrm{BaO}_2 \), is a compound made of barium and oxygen. Barium is an element located in Group 2 of the periodic table, classified as an alkaline earth metal. Its common oxidation state is \(+2\). In \( \mathrm{BaO}_2 \), each oxygen atom typically takes an oxidation state of \(-1\) instead of the usual \(-2\) found in most oxides. This is due to the peroxide linkage present in barium peroxide, where oxygen atoms are bonded together.
Barium peroxide is a white crystalline solid at room temperature and is often used as a precursor in chemical reactions to release oxygen. It plays an important role in generating hydrogen peroxide when it reacts with dilute sulfuric acid.

• Silver-colored and highly reactive metal
• Primarily exists in the oxidation state of \(+2\)
• Participates in reactions as an oxidizing agent due to the peroxide ion

Hydrogen Peroxide

Hydrogen peroxide, symbolized as \( \mathrm{H}_2 \mathrm{O}_2 \), is a simple peroxide with interesting properties. Unlike water, which has oxygen in the usual \(-2\) oxidation state, hydrogen peroxide has oxygen at a \(-1\) oxidation state because of the -O-O- linkage called the peroxide bond.
This compound is a clear, colorless liquid and is commonly used as a disinfectant, bleaching agent, and in some cases, as a propellant in rocketry. Its chemical reactivity is chiefly due to the unstable peroxide bond, making it a strong oxidizing agent, which can be harnessed for various applications.

• Has a molecular formula of \( \mathrm{H}_2 \mathrm{O}_2 \)
• Functions as an oxidizer and sometimes a reducing agent
• Highly unstable and can release oxygen rapidly

Electronegativity

Electronegativity is a fundamental concept in chemistry, referring to the ability of an atom to attract shared electrons in a chemical bond. It often influences the type of bond formed and the polarity inherent in chemical compounds.
In the context of the exercise, oxygen is the most electronegative element involved in the reaction between barium peroxide and sulfuric acid. With an electronegativity value typically higher than many other elements, oxygen tends to pull electrons toward itself, impacting its oxidation states in various compounds.

• A critical factor in determining bond type and strength
• Varies across the periodic table, with fluorine being the most electronegative element
• Determines the oxidation state in a compound

Balancing Chemical Reactions

Balancing chemical reactions is essential to ensure that the same number of atoms of each element are on both sides of the equation. This balances the mass and adheres to the law of conservation of mass.
The balanced reaction between barium peroxide and sulfuric acid is: \( \mathrm{BaO}_2 + \mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4 + \mathrm{H}_2 \mathrm{O}_2 \). This shows a proper transformation from reactants to products, keeping in mind that the elements rearrange but do not change mass.

• Crucial for quantitative chemical analysis and experiments
• Involves adjusting coefficients to match the number of each type of atom
• Ensures that chemical equations comply with the law of conservation of mass