Problem 38 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is produced, when copper reacts with chlorine? (a) \(\mathrm{CuCl}_{4}\) (b) \(\mathrm{Cu}_{2} \mathrm{Cl}\) (c) \(\mathrm{Cu}_{2} \mathrm{Cl}_{2}^{4}\) (d) \(\mathrm{CuCl}_{2}\)

Step-by-Step Solution

Answer

Copper reacts with chlorine to produce \\( ext{CuCl}_2 \\).

Step 1: Understanding the Reactants

Before we solve the question, let's identify the reactants in the reaction. The reactants are copper (Cu) and chlorine (Cl). Copper is a metal, and chlorine is a non-metal.

Step 2: Determining Copper's Common Oxidation States

Copper commonly exists in two oxidation states: +1 and +2. This will help us predict the possible compounds that can form when copper reacts with chlorine.

Step 3: Pairing Copper and Chlorine

Copper with an oxidation state of +1 can pair with chlorine to form \( ext{Cu}_2 ext{Cl}_2\), and copper with an oxidation state of +2 can pair with chlorine to form \( ext{CuCl}_2\). From the list given, \( ext{CuCl}_2\) corresponds to copper's +2 oxidation state pairing with two chlorine atoms.

Step 4: Evaluating Given Options

For the given options:- \( CuCl_4 \) does not exist as a common compound.- \( Cu_2Cl \) has incorrect stoichiometry.- \( Cu_2Cl_2^4 \) does not exist due to incorrect notation.- \( CuCl_2 \) is the correct formula for the compound formed when copper ions in +2 oxidation state react with chlorine ions.

Key Concepts

Oxidation States of Copper

Copper is a fascinating metal known for its ability to exhibit different oxidation states. Primarily, copper exists in two oxidation states: +1 and +2. This is important because the oxidation state of an element dictates how it will interact with other elements in chemical reactions. Essentially, the oxidation state is a measure of the degree of oxidation of an atom within a compound.

• In the +1 oxidation state, copper is referred to as cuprous, and it is less stable compared to the +2 oxidation state.
• In the +2 oxidation state, copper is known as cupric, and this state is more commonly found in nature and chemical reactions.

Understanding the oxidation states of copper helps in predicting the type of compounds it can form, such as whether it will bond with one atom of chlorine or two.

Copper Compounds

Copper forms a wide range of compounds, typically depending on its oxidation state. These compounds are vital in various industrial applications and daily life. The type of copper compound formed with chlorine will depend on the copper’s oxidation state during the reaction.

• When copper is in the +1 oxidation state, it usually forms compounds like copper(I) chloride, written as \( \mathrm{Cu}_{2}\mathrm{Cl}_{2} \), where two copper atoms bond with two chlorine atoms.
• In the +2 oxidation state, copper pairs with chlorine as \( \mathrm{CuCl}_{2} \), forming copper(II) chloride, commonly used in various applications, including as a catalyst and in pigments.

The formation of these copper compounds is a classic example of how chemical processes rely on the oxidation state to dictate how atoms bond in a compound.

Chemical Reactions

Chemical reactions involve the transformation of reactants into products through the breaking and forming of bonds. When considering a reaction between copper and chlorine, this process is dictated by how these elements' electrons interact. Copper, being a metal, will lose electrons, while chlorine, a non-metal, tends to gain electrons in reactions.

• This interchange of electrons results in the formation of an ionic bond, which is common when metals and non-metals react.
• The specific compound formed in this reaction will depend on the electron transfer resulting in either copper(I) chloride or copper(II) chloride, depending mainly on the oxidation state of copper.

The resulting compounds are stable or reactive depending on the arrangement of their constituent atoms and the specific conditions under which they form.

Stoichiometry in Chemistry

Stoichiometry is the study of the quantitative relationships in chemical reactions. It allows chemists to predict how much of a substance will react or be produced in a given reaction. This is especially important in understanding reactions like that of copper and chlorine.

• By applying stoichiometry, one can balance the chemical equation for the reactions involving copper and chlorine. It shows the proportion of reactants needed to form a specific product.
• The stoichiometric coefficients help determine how many moles of copper and chlorine are required to form the various copper chloride compounds.

Understanding stoichiometry ensures that reactions are represented correctly and is a fundamental tool for chemists in both research and industry.