Chemical Bonds and Energy Worksheet

Part 1: Chemical Bonds and Energy Storage

1.1) Define what a chemical bond is.


1.2) Explain how each of the following types of chemical bonds forms:

a) Ionic bond

b) Covalent bond


c) Hydrogen bond

1.3) How does a chemical bond store energy? Explain using an example.





1.4) Consider the bond in a hydrogen molecule (H₂). Draw a simple energy diagram that shows the potential energy of the atoms as they approach each other to form a bond.

Part 2: Exothermic vs. Endothermic Reactions

2.1) Define the following terms:

a) Exothermic reaction


b) Endothermic reaction

2.2) For each reaction below, determine whether it is exothermic or endothermic:

a) $$ CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O + \text{energy} $$

b) $$ \text{energy} + N_2 + 3H_2 \rightarrow 2NH_3 $$

c) $$ \text{energy} + 6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2 $$

2.3) Draw energy diagrams for a typical exothermic and endothermic reaction. Label the reactants, products, activation energy, and change in enthalpy (ΔH).

2.4) The combustion of methane releases 890 kJ/mol of energy. Write a balanced thermochemical equation for this reaction.

Part 3: Conservation of Energy in Chemical Reactions

3.1) State the Law of Conservation of Energy and explain how it applies to chemical reactions.

3.2) In the reaction $$A + B \rightarrow C + D$$, 50 kJ of energy is released. If the reverse reaction $$C + D \rightarrow A + B$$ were to occur, how much energy would be involved? Explain your answer.

3.3) A student claims that some energy is lost during a chemical reaction. Explain why this statement is incorrect.

3.4) The formation of 1 mole of liquid water from hydrogen and oxygen gases releases 286 kJ of energy: $$H_2(g) + \frac{1}{2}O_2(g) \rightarrow H_2O(l) \quad \Delta H = -286 \text{ kJ/mol}$$

How much energy is required to decompose 2 moles of liquid water into hydrogen and oxygen gases?

Part 4: Bond Breaking and Bond Formation

4.1) Complete the following table:

4.2) The energy required to break all bonds in the reactants is 1500 kJ/mol. The energy released when new bonds form in the products is 1800 kJ/mol. Calculate the overall energy change for this reaction and determine if it is endothermic or exothermic.

4.3) Calculate the enthalpy change for the following reaction using bond energies: $$CH_4 + Cl_2 \rightarrow CH_3Cl + HCl$$

Use the following bond energies: - C-H bond: 413 kJ/mol - Cl-Cl bond: 242 kJ/mol - C-Cl bond: 328 kJ/mol - H-Cl bond: 431 kJ/mol

4.4) Explain why most combustion reactions are exothermic in terms of bond breaking and bond formation.

Part 5: Application Questions

5.1) Photosynthesis is an endothermic process, while cellular respiration is exothermic. Explain how these processes relate to each other in terms of energy flow.

5.2) When a cold pack is activated, ammonium nitrate dissolves in water, making the pack feel cold. Explain this phenomenon using your knowledge of endothermic and exothermic processes.

5.3) Design an experiment to determine whether a chemical reaction is endothermic or exothermic. Include the materials needed, procedure, and how you would analyze the results.

5.4) Research and explain one real-world application where understanding bond energy is important.