Question

Which statement is true of an endothermic reaction? a. Strong bonds break and weak bonds form. b. Weak bonds break and strong bonds form. c. The bonds that break and those that form are of approximately the same strength.

Short answer

The correct statement for an endothermic reaction is b. Weak bonds break and strong bonds form, as these reactions absorb energy.

Step-by-step solution

Understanding Endothermic Reactions

Endothermic reactions are chemical reactions in which the system absorbs energy from its surroundings. This typically occurs when the energy needed to break the bonds in the reactants is greater than the energy released when new bonds are formed in the products.

Analyzing the Options

To determine which statement is true for an endothermic reaction, compare the energy of bonds being broken with the energy of bonds being formed. In an endothermic reaction, the energy required to break existing bonds is higher than the energy released by forming new bonds.

Identifying the Correct Statement

Considering the higher energy requires to break bonds and the lower energy release upon forming new bonds, the correct statement for an endothermic reaction is the one that indicates that weak bonds are breaking resulting in the formation of stronger bonds which require more energy to form than is released during the formation.

Key concepts

Bond Energy in Chemical Reactions

Bond energy refers to the amount of energy required to break one mole of bonds in a substance in the gaseous state. It's a crucial concept in understanding chemical reactions, as it determines the strength of different chemical bonds.

In endothermic reactions, bonds with lower bond energy, known as 'weak' bonds, break to form stronger bonds that have higher bond energy requirements. This is because breaking a chemical bond takes energy from the surroundings, and forming a new bond releases energy. However, if formation of the new bond does not release as much energy as is taken in to break the original bonds, the overall process requires an input of energy. This discrepancy is the core aspect of endothermic reactions, where the net energy absorbed from the environment causes a temperature decrease in the surrounding area.

For example, when ice melts, energy is absorbed from the environment to break the hydrogen bonds between the water molecules. This process is an endothermic reaction because more energy is used to separate the molecules than is released.

Energy Absorption in Chemical Processes

When delving into chemical processes, energy absorption is a pivotal concept, particularly in endothermic reactions. An endothermic reaction cannot occur without absorbing energy, which usually comes in the form of heat, from its environment.

The absorbed energy facilitates the breaking apart of the molecular bonds within the reactants. It’s the initial input of energy that triggers the chemical transformation. As such, understanding energy absorption is critical for grasping why certain reactions are endothermic. In the context of our exercise, the key aspect to remember is that endothermic reactions imply a net flow of energy into the system, making the bonds that form stronger - and consequently, with higher bond energies - than the ones that break.

To apply this to a real-world instance, consider photosynthesis, where plants absorb sunlight to convert carbon dioxide and water into glucose and oxygen. This energy absorption is quintessential to the process, as it powers the conversion, illustrating energy absorption's role in facilitating endothermic reactions.

Chemical Bonds

Chemical bonds are the glue that holds atoms together in molecules. They are formed through the sharing or transferring of electrons between atoms, creating a stable arrangement. There are three primary types of chemical bonds: ionic, covalent, and metallic.

Understanding the different types of chemical bonds is essential for predicting the properties of compounds and the outcomes of chemical reactions. In endothermic reactions, such as in our textbook exercise, the focus is on breaking and forming covalent bonds, where electrons are shared between atoms.

The nature of the chemical bonds involved changes during the reaction, transforming weaker bonds into stronger ones. This transformation requires energy input because forming a stronger bond typically involves lowering the potential energy between the atoms, which, paradoxically, requires an initial energy investment. Thus, in endothermic processes, it’s the energy that went into creating the stronger bonds that leads to an overall absorption of energy.