Question

Write this reaction in terms of formation reactions. $$ 2 \mathrm{CuCl}(\mathrm{s}) \rightarrow \mathrm{Cu}(\mathrm{s})+\mathrm{CuCl}_{2}(\mathrm{~s}) $$

Short answer

The reaction is composed of the formation reactions of CuCl and CuCl2 from their elements.

Step-by-step solution

Identify the Products and Reactants

In the given reaction, the reactants are 2 moles of solid copper(I) chloride, represented as \(2 \mathrm{CuCl} (\mathrm{s})\). The products are solid copper, \(\mathrm{Cu} (\mathrm{s})\), and solid copper(II) chloride, \(\mathrm{CuCl_2} (\mathrm{s})\).

Define Formation Reactions for Products

A formation reaction forms one mole of a compound from its elements in their standard states. Therefore, for \(\mathrm{Cu} (\mathrm{s})\), the formation reaction is trivial: \[ \mathrm{Cu(s)} \rightarrow \mathrm{Cu(s)} \] For \(\mathrm{CuCl_2} (\mathrm{s})\), it forms from solid copper and chlorine gas: \[ \mathrm{Cu(s)} + \mathrm{Cl_2(g)} \rightarrow \mathrm{CuCl_2(s)} \] The standard formation state of chlorine is \(\mathrm{Cl_2(g)}\) and copper is \(\mathrm{Cu(s)}\).

Write Formation Reaction for Reactant

\(\mathrm{CuCl} (\mathrm{s})\), which appears as a reactant, forms from its constituent elements: copper and chlorine gas. The formation reaction is: \[ \mathrm{Cu(s)} + \frac{1}{2} \mathrm{Cl_2(g)} \rightarrow \mathrm{CuCl(s)} \]

Combine Formation Reactions for Original Reaction

Since the original reaction is: \[ 2 \mathrm{CuCl(s)} \rightarrow \mathrm{Cu(s)} + \mathrm{CuCl_2(s)} \]To represent it using formation reactions:1. Reverse and multiply the formation reaction of \(\mathrm{CuCl} (\mathrm{s})\) by 2: \[ 2 \times (\mathrm{CuCl(s)} \rightarrow \mathrm{Cu(s)} + \frac{1}{2} \mathrm{Cl_2(g)}) \]2. Use the direct formation reactions for the products.This results in:\[ 2 \mathrm{Cu(s)} + \mathrm{Cl_2(g)} \rightarrow 2 \mathrm{CuCl(s)} \] for the reactant side and: \[ \mathrm{Cu(s)} + \mathrm{Cl_2(g)} \rightarrow \mathrm{CuCl_2(s)} \]for \(\mathrm{CuCl_2(s)}\).

Key concepts

Chemical Reactions

Chemical reactions involve the transformation of substances through the breaking and forming of chemical bonds. In a chemical reaction, reactants are converted into products. The equation given: \[ 2 \mathrm{CuCl}(\mathrm{s}) \rightarrow \mathrm{Cu}(\mathrm{s}) + \mathrm{CuCl}_2 (\mathrm{s}) \] involves the decomposition of copper(I) chloride into solid copper and copper(II) chloride. Understanding the stoichiometry, which is the quantitative relationship between reactants and products, is crucial. This allows us to correctly balance chemical equations and ensure that the mass and charge are conserved during the reaction.

To analyze such reactions, we can express them in terms of formation reactions, where compounds are formed from their basic elements in standard states. Formation reactions assist in determining reaction enthalpies and other thermodynamic properties. They simplify the complexities of chemical reactions by breaking them into simpler steps involving element combinations.

Copper Compounds

Copper compounds, like copper(I) chloride \(\mathrm{CuCl}\) and copper(II) chloride \(\mathrm{CuCl}_2\), have unique properties and different oxidation states. These features are critical in dictating their chemical behaviors.
- **Copper(I) Chloride:** Also known as cuprous chloride, this compound has copper in a +1 oxidation state. It is less stable compared to its counterpart, copper(II) chloride. Its standard formation is characterized by the reaction: \[ \mathrm{Cu(s)} + \frac{1}{2} \mathrm{Cl_2(g)} \rightarrow \mathrm{CuCl(s)} \]- **Copper(II) Chloride:** Known as cupric chloride, it holds copper in a +2 oxidation state and forms when copper interacts with chlorine: \[ \mathrm{Cu(s)} + \mathrm{Cl_2(g)} \rightarrow \mathrm{CuCl_2(s)} \]
Understanding these different copper compounds helps in predicting and explaining various chemical processes and reactions, particularly those involving electron transfer and changes in oxidation states.

Standard States

Standard states refer to the most stable states of substances under specified conditions, typically at 1 atmosphere of pressure and a predefined temperature, usually 25°C (298 K). For gases, this often means pure gas at 1 atm; for solids and liquids, it's the pure form under the same pressure.
- **Copper's Standard State:** The element exists in its solid form \(\mathrm{Cu(s)}\) under standard conditions, which is its most stable form. - **Chlorine's Standard State:** Chlorine exists as a diatomic gas \(\mathrm{Cl_2(g)}\) at room temperature and pressure.
Formation reactions are greatly influenced by these standard states as they serve as reference points for calculating thermodynamic quantities like enthalpies of formation. Knowing these states aids in developing, analyzing, and synthesizing chemical reactions more effectively.