Question

Write a chemical equation for the reaction between methane and bromine.

Short answer

\( \text{CH}_4 + \text{Br}_2 \rightarrow \text{CH}_3\text{Br} + \text{HBr} \)

Step-by-step solution

Identify Reactants

The reactants in the chemical reaction are methane (\(\text{CH}_4\)) and bromine (\(\text{Br}_2\)). Methane is a simple alkane with one carbon atom, and bromine is a diatomic molecule.

Predict the Products

In a halogenation reaction between an alkane and a halogen, the hydrogen atom of the alkane is replaced by the halogen. For methane and bromine, the product is bromomethane (\(\text{CH}_3\text{Br}\)) and hydrogen bromide (\(\text{HBr}\)).

Write the Unbalanced Equation

Write down the unbalanced chemical equation for the reaction: \( \text{CH}_4 + \text{Br}_2 \rightarrow \text{CH}_3\text{Br} + \text{HBr} \).

Balance the Chemical Equation

Ensure both sides of the equation have an equal number of each type of atom. The unbalanced equation has 1 carbon, 4 hydrogens, and 2 bromines on the left side, and 1 carbon, 3 hydrogens, and 2 bromines on the right side. To balance the hydrogens, no changes are needed, as they are balanced by \text{CH}_4 and \text{HBr\ on the right. The equation is already balanced with 1 \(\text{CH}_4\), 1 \(\text{Br}_2\), 1 \(\text{CH}_3\text{Br}\), and 1 \(\text{HBr}\).

Write the Balanced Chemical Equation

The balanced chemical equation for the reaction between methane and bromine is: \( \text{CH}_4 + \text{Br}_2 \rightarrow \text{CH}_3\text{Br} + \text{HBr} \).

Key concepts

Understanding Halogenation Reactions

A halogenation reaction is a type of chemical reaction where a halogen atom is introduced into a molecule, typically replacing a hydrogen atom. This kind of reaction occurs most commonly with alkanes like methane. Halogens are elements found in Group 17 of the periodic table, including fluorine, chlorine, bromine, and iodine. These elements are highly reactive due to their seven valence electrons, which make them eager to gain an eighth electron to complete their outer shell.

• During halogenation, the alkane molecule undergoes a substitution reaction, where one or more of its hydrogen atoms are replaced by halogen atoms.
• This process often requires energy input, such as ultraviolet light or heat, to initiate the reaction.
• The result of this reaction is the formation of a halogenated alkane and a hydrogen halide.

Understanding halogenation reactions is crucial because they are used extensively in organic chemistry to synthesize new compounds with desired properties. They serve as a fundamental method for modifying organic molecules.

Balancing Chemical Equations

Balancing chemical equations is essential to accurately represent the conservation of mass in a chemical reaction. It ensures that the number of atoms of each element is the same on both sides of the equation. This reflects the principle that matter cannot be created or destroyed, only rearranged.

• The process involves adjusting the coefficients, which are the numbers placed before the chemical formulas in the equation.
• These coefficients are used to multiply the number of molecules or moles of a substance in the reaction.
• While balancing, one must check each element in sequence and make sure the count is the same on both reactant and product sides.

For example, when balancing the reaction between methane and bromine, we ensure there is one carbon atom, four hydrogen atoms, and two bromine atoms on both sides of the equation. This guarantees correctness and adherence to the conservation laws.

The Methane and Bromine Reaction

The specific reaction between methane and bromine is a classic example of a halogenation reaction. Methane (\(\text{CH}_4\)) is a simple hydrocarbon, consisting of one carbon atom bonded to four hydrogen atoms. Bromine (\(\text{Br}_2\)) is a diatomic molecule, meaning it consists of two bromine atoms.

• When these two react, the result is the substitution of one hydrogen atom from methane, with one bromine atom from the bromine molecule.
• This forms bromomethane (\(\text{CH}_3\text{Br}\)) and hydrogen bromide (\(\text{HBr}\)) as products.
• The balanced chemical equation for this reaction is: \(\text{CH}_4 + \text{Br}_2 \rightarrow \text{CH}_3\text{Br} + \text{HBr}\).

This equation symbolizes the conservation of mass, where the amounts of each type of atom at the start (reactants) are the same as those in the products, achieved by balancing the chemical equation. This reaction is a building block for understanding more complex chemical processes.