Problem 44 - A Complete Resource Book in Chemistry for JEE Main

Question

What is produced when cuprous oxide reacts with HCl? (a) \(\mathrm{CuCl}\) (b) \(\mathrm{CuO}\) (c) \(\mathrm{HCuCl}_{2}\) (d) \(\mathrm{CuCl}_{2}\)

Step-by-Step Solution

Answer

(a) \( \mathrm{CuCl} \) is produced.

Step 1: Identify the Reactants

The reactants in this chemical reaction are cuprous oxide (3 ext{o}_{2}5 ext{Cu}$_2$3 ext{o}) and hydrochloric acid (3 ext{HCl}).

Step 2: Determine the Oxidation States

Cuprous oxide (3 ext{o}_{2}5 ext{Cu}$_2$3 ext{o}) contains copper in the +1 oxidation state, and hydrochloric acid contains hydrogen in the +1 oxidation state and chlorine in the -1 oxidation state.

Step 3: Predict the Products

When cuprous oxide reacts with hydrochloric acid, copper will form copper(I) chloride (3 ext{u}_{2}5 ext{CuCl}), and water (3 ext{O}) will be produced along with it. The balanced equation is: 3 ext{o}_{2}5 ext{Cu}$_2$3 ext{o} + 2 3 ext{HCl} 3 ext{u}_{2}5 ext{CuCl} + 3 ext{H}_{2}5 ext{o}}.

Step 4: Compare with the Given Options

The reaction forms copper(I) chloride (3 ext{u}_{2}5 ext{CuCl}), which matches option (a) 3 ext{u}_{2}5 ext{CuCl}.

Key Concepts

Cuprous Oxide

Cuprous oxide is a fascinating compound with the chemical formula \( \text{Cu}_2\text{O} \). This compound contains copper in the +1 oxidation state, distinguishing it from cupric compounds where copper exists in the +2 state. When learning about cuprous oxide, it's important to note its composition:

• It is one of several stable copper oxides and is often red or reddish-brown in color.
• It's used in various applications including pigments, fungicides, and semiconductors, due to its unique properties.

Cuprous oxide's behavior in chemical reactions is determined by its oxidation state. Here, copper's +1 oxidation state implies that each copper ion shares an electron with another, paired with an oxygen atom, allowing it to readily participate in redox reactions. Understanding how cuprous oxide interacts with other substances is crucial in predicting reactions in which it is involved.

Hydrochloric Acid

Hydrochloric acid is a strong, corrosive acid composed of hydrogen chloride in aqueous solution with the formula \( \text{HCl} \). It is characterized by its:

• Strong acidic nature, fully dissociating in water to release hydrogen ions, \( \text{H}^+ \), and chloride ions, \( \text{Cl}^- \).
• Common applications in various industries, including chemical production, food processing, and metal refining.
• Low pH, making it ideal for cases where a powerful acid is necessary.

In the context of reacting with cuprous oxide, hydrochloric acid provides the necessary medium to facilitate the chemical reaction, acting as a source of chloride ions. This acid allows cuprous oxide to break down into copper(I) chloride, a different compound where copper maintains its +1 oxidation state.

Oxidation States

Oxidation states, or oxidation numbers, are integer values that describe the effective charge of an atom in a compound. They help in determining how electrons are distributed among the atoms in molecules. In this framework:

• Cuprous oxide features copper in a +1 oxidation state, indicating each copper atom has lost one electron in the formation of the oxide.
• In hydrochloric acid, hydrogen is in the +1 oxidation state, offering its electron toward a covalent bond, while chlorine maintains a -1 state, gaining an electron.

Understanding oxidation states is crucial when predicting the products of a chemical reaction. In reactions, these states help identify which elements are oxidized or reduced, enabling us to write balanced chemical equations accurately. Such equations reflect the transfer of electrons—integral to comprehending changes in the substances' chemical structure during reactions.