Question

For the reaction \(\mathrm{H}_{2}(g)+\mathrm{Br}_{2}(g) \rightarrow 2 \mathrm{HBr}(g),\) list the types of bonds that must be broken and the type of bond that must form in order for the chemical reaction to take place.

Short answer

In the given reaction, one single covalent bond each in \( \mathrm{H}_2 \) and \( \mathrm{Br}_2 \) must be broken. To form the product \( \mathrm{HBr} \), a new single covalent bond must be created between hydrogen and bromine atoms.

Step-by-step solution

Identify the types of bonds in reactants

In the given chemical reaction, hydrogen gas \( (\mathrm{H}_2) \) and bromine gas \( (\mathrm{Br}_2) \) are the reactants. Hydrogen gas is composed of two hydrogen atoms bonded together, and bromine gas is composed of two bromine atoms bonded together. In both cases, the bond that holds the atoms together is a single covalent bond. So, in order to proceed with the reaction, one covalent bond each in hydrogen gas and bromine gas must be broken.

Identify the type of bond in the product

The product of the given chemical reaction is hydrogen bromide gas \( (2 \mathrm{HBr}) \). Hydrogen bromide consists of one hydrogen atom and one bromine atom bonded together. The bond that holds these atoms together is also a single covalent bond. Therefore, in order to form the product, a new single covalent bond must be formed between the hydrogen and bromine atoms.

Summarize the bond breaking and forming processes

In the given chemical reaction, a single covalent bond in hydrogen gas and a single covalent bond in bromine gas must be broken for the reaction to take place. After breaking these bonds, a new single covalent bond must form between the hydrogen and bromine atoms to produce hydrogen bromide gas.

Key concepts

Understanding Covalent Bonds

Covalent bonds are a fundamental concept in chemistry. They occur when two atoms share one or more pairs of electrons. This sharing allows each atom to fill its outer electron shell, achieving a more stable electronic configuration. In the reaction between hydrogen gas \(\mathrm{H}_2\) and bromine gas \(\mathrm{Br}_2\), each gas features diatomic molecules where two atoms are linked by covalent bonds.

• Hydrogen Molecules: In \(\mathrm{H}_2\), two hydrogen atoms share one pair of electrons, forming a single covalent bond.
• Bromine Molecules: Similarly, in \(\mathrm{Br}_2\), two bromine atoms are also joined by a single covalent bond, sharing one pair of electrons.

Understanding how these covalent bonds work is crucial in predicting how chemical reactions will proceed. Covalent bonds are significant because they define how atoms stay together in a molecule and determine the molecule's chemical properties.

Exploring Reaction Mechanisms

The reaction mechanism is the step-by-step sequence of events that describes how a chemical reaction occurs. For the reaction \(\mathrm{H}_2(g) + \mathrm{Br}_2(g) \rightarrow 2\mathrm{HBr}(g)\),the process involves a series of bond-breaking and bond-forming stages. Understanding the mechanism helps to visualize the movement of electrons and atoms.

Step 1: Initiation - The initial step requires energy to break the covalent bonds in both hydrogen \(\mathrm{H}_2\) and bromine \(\mathrm{Br}_2\). These are the activation steps needed to kickstart the reaction.

Step 2: Bond Formation - After bond breaking, new bonds form between hydrogen and bromine atoms to create \(\mathrm{HBr}\) molecules. This step releases energy, often making the reaction energetically favorable.

Reaction mechanisms often include intermediate entities and transition states that are crucial for completing the process. Observing how bonds break and form at the molecular level unveils the complexity and elegance of chemical reactions.

Bond Breaking and Forming Dynamics

Bond breaking and forming are the core phenomena in chemical reactions. In our specific reaction, the breakdown of molecules and the formation of new bonds change the chemical identity of the substances involved.

• Bond Breaking: Breaking bonds in \(\mathrm{H}_2\)and \(\mathrm{Br}_2\)requires energy. This is because covalent bonds hold considerable energy to keep the atoms together.
• Bond Forming: When new covalent bonds form between hydrogen and bromine to make hydrobromic acid \(\mathrm{HBr}\), energy is released. This release often helps drive the reaction forward.

The overall energy changes depend on the balance between the energy required to break old bonds and the energy released from forming new ones. Understanding these energy dynamics is key to predicting reaction outcomes and is fundamental to studying chemical thermodynamics and kinetics.