Question

Carbon tetrachloride was widely used for many years as a solvent until its harmful properties became well established. Carbon tetrachloride may be prepared by the reaction of natural gas (methane, \(\mathrm{CH}_{4}\) ) and elemental chlorine gas in the presence of ultraviolet light. Write the unbalanced chemical equation for this process.

Short answer

The unbalanced chemical equation for the formation of carbon tetrachloride (\(\mathrm{CCl}_{4}\)) from methane (\(\mathrm{CH}_{4}\)) and chlorine gas (\(\mathrm{Cl}_{2}\)) in the presence of ultraviolet light is: \[\mathrm{CH}_{4} + \mathrm{Cl}_{2} \xrightarrow{\text{UV light}} \mathrm{CCl}_{4}\]

Step-by-step solution

Identify the reactants and the product

The reactants are methane (\(\mathrm{CH}_{4}\)) and chlorine gas (\(\mathrm{Cl}_{2}\)). The product is carbon tetrachloride (\(\mathrm{CCl}_{4}\)).

Write the unbalanced chemical equation for this process.

The unbalanced chemical equation for the reaction of methane with chlorine gas in the presence of UV light to form carbon tetrachloride is: \[\mathrm{CH}_{4} + \mathrm{Cl}_{2} \xrightarrow{\text{UV light}} \mathrm{CCl}_{4}\]

Key concepts

Unbalanced Chemical Equation

Chemical reactions often begin as unbalanced equations, which means the number of atoms for each element does not match between the reactants and the products. To understand this process, imagine a simple scales, where the goal is balance. In a balanced chemical equation, each side of the equation has the same number of atoms of each element. This represents the conservation of mass in a chemical reaction. An unbalanced chemical equation does not meet this criterion and needs to be adjusted.
In the context of the exercise, the given unbalanced equation is: \(\mathrm{CH}_{4} + \mathrm{Cl}_{2} \xrightarrow{\text{UV light}} \mathrm{CCl}_{4}\). Here, the challenge is to balance the equation by possibly altering the coefficients of the reactants or products. Remember, only the coefficients (the numbers in front of molecules) can be changed, not the subscripts (numbers within a chemical formula). Balancing ensures that the number of each type of atom is the same on both sides of the equation.

Methane

Methane, with the chemical formula \(\mathrm{CH}_{4}\), is a simple alkane and the main component of natural gas. It consists of one carbon atom bonded to four hydrogen atoms, forming a tetrahedral shape. Methane plays a crucial role as a fuel source due to its abundance and high energy content.
Methane is not just a significant fuel but also a powerful greenhouse gas. Understanding its structure and properties can help in creating cleaner technologies. In the exercise, methane acts as a reactant with chlorine gas to produce carbon tetrachloride. The reaction happens under ultraviolet light, emphasizing the importance of energy in chemical transformations.

Chlorine Gas

Chlorine gas, \(\mathrm{Cl}_{2}\), is a diatomic molecule consisting of two chlorine atoms. It has a pale yellow-green color and a distinct pungent odor. Chlorine is highly reactive, especially with organic compounds, making it useful in a wide range of chemical processes.
Because of its reactivity, chlorine gas is often used in disinfecting and bleaching applications. However, in the presence of ultraviolet light, it can participate in reactions such as the formation of carbon tetrachloride. During the reaction with methane, chlorine molecules break down, allowing chlorine atoms to bond with carbon atoms to form new compounds.

Carbon Tetrachloride

Carbon tetrachloride, \(\mathrm{CCl}_{4}\), is a compound known for its past use as a fire extinguisher and in dry cleaning. It is a colorless, volatile liquid with a sweet odour. Structurally, carbon tetrachloride consists of a single carbon atom bonded to four chlorine atoms, creating a symmetrical tetrahedral shape.
Despite its practical applications, carbon tetrachloride is hazardous, being both toxic and a potential carcinogen. Its use diminished significantly as its harmful effects became more understood, especially on human health and the environment. In the context of the chemical reaction with methane and chlorine gas, carbon tetrachloride is the main product formed, illustrating the transformation of simpler molecules into more complex ones.