Bond Energy Questions and Answers

Bond energy (B.E) is one of the important parameters in chemistry that is responsible for measuring strength of a chemical bond. The standard unit of B.E is Kilojoules per mole (KJ/mol).

• Bond energy also called bond dissociation energy, can be explained by the energy required to break one mole of bond.
• Stability of molecules and their reactivity can be determined by understanding bond energy. 

There are some important questions related to bond energy important for students preparing for their board exams or NEET and JEE exams are mentioned below: 

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Conceptual Questions

In this section, we have covered mainly textbook based questions which are frequently asked in board exams, and in viva. 

Ques. What is bond energy in chemistry?

Ans. Bond energy is an important bond parameter that describes the amount of energy required to break a chemical bond. The calculation of bond energy is helpful in determining the strength of a bond.

Ques. Can bond energy and bond dissociation energy become equal? Explain with reasons. 

Ans. Bond energy and bond dissociation becomes equal in diatomic molecules or in gaseous state such as O2, H2, etc.

• Bond dissociation energy is the amount of energy needed to split a molecule into two equal parts by breaking an existing bond. 
• On the other hand, the average values of all bond dissociation energy in a molecule are called bond energy which is the same for all diatomic molecules. 

Ques. What are the important factors that influence the bond energy? 

Ans. Here are some important factors that influence bond energy mentioned below-

• Bond Order: In comparison to single bonds, the bond energies of multiple bonds (double, triple) are more. 
• Bond Length: The bond energies of shorter bonds are always high and more strong. 
• Electronegativity: The bond energies of high electronegative elements are always higher than that of less electronegative elements. 

Ques. What are the methods used for calculating bond energy?

Ans. Thermochemical cycles and Hess's Law can be used to determine bond energy. For experimental estimation of bond energy, the change in bond enthalpy is recorded. The bond energies of both reactants and products are taken into consideration while calculating total energy change in a reaction.

Ques. How is the understanding of bond energy useful in real life?

Ans. A proper understanding of bond energy is very useful in various fields of science such as material science, chemical reactions, environmental science, etc. Apart from this, there are some real-life applications of bond energy which are mentioned below-

• With an appropriate knowledge of bond energies, scientists can easily figure out the type of bonds in a reaction which are most likely to break and form. 
• A knowledge of bond energy is helpful to make materials that have good strength and endurance.
• Understanding bond energies is essential in determining how biological systems' enzymes degrade their substrates.

Ques. What are the trends in bond energy in the periodic table?

Ans. The bond energy trends in the periodic table is given as: 

• The bond energy decreases with the increase in atomic size down the group. 
• There is a direct relationship between the bond energy and effective nuclear charge. 
• So, as the effective nuclear charge across the period increases, bond energy also increases. 

Ques. What is the bond energy of water and what is its significance?

Ans. The O-H bond in water forms a hydrogen bond and its bond energy is estimated as 463 kJ/mol experimentally. The value implies the strong bond between hydrogen and oxygen which further contributes to high boiling point, surface tension and other peculiar characteristics of water. 

Ques. How is a chemical reaction's rate impacted by bond energy?

Ans. The amount of energy that can be transformed into activation energy in a collision increases with temperature, which can speed up the rate of reaction. In simple words, as the rate of reaction increases, bond energy also increases. 

Ques. How does bond energy change with electronegativity?

Ans. Electronegativity is an important parameter that influences the bond energy. A high electronegative element can strongly bind to other elements as compared to a less electronegative element. 

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Bond Energy MCQs

In this section, we have discussed numerical based and other sample questions asked in various competitive exams such as NEET, JEE, IIT JAM, etc. 

Ques. Find the change in bond enthalpy in the following reaction: 

C2H6 +Cl2 —→C2H5Cl +HCl if the given values are: 

The bond enthalpy of C–H = 413 KJ/mol, Cl-Cl = 239 KJ/mol, C–Cl = 339 KJ/mol, H–Cl= 427 KJ/mol

1. +114 KJ/mol
2. -114 KJ/mol
3. +1418 KJ/mol
4. -1418 KJ/mol

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Ques. How is the melting point of solid affected by bond energy?

1. As the melting point increases, bond energy decrease
2. As the melting point increases, bond energy remains constant
3. As the melting point increases, the bond energy first increases and then decreases
4. As the melting point increases, bond energy also increases

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Ques. Which of the following molecules has non-zero dipole moment?

1. H₂O
2. BeF₂
3. N₂
4. CH₄

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