Question 1: Bond energy is the amount of energy required to break one mole of a specific type of bond in a gaseous molecule. It is usually measured in kilojoules per mole (kJ/mol). Understanding bond energies helps us determine whether a chemical reaction releases or absorbs energy.

Answer: Bond energy is the energy needed to break one mole of a specific bond in a gaseous molecule; it indicates the strength of a chemical bond.

Question 1: Given that the bond energies for H-H, Cl-Cl, and H-Cl are 436 kJ/mol, 243 kJ/mol, and 431 kJ/mol respectively, calculate the overall energy change for the reaction: H₂ + Cl₂ → 2 HCl. Show your calculations.

Answer: Energy change = (Bond energies of bonds broken) - (Bond energies of bonds formed); Calculation: (436 + 243) - (2 × 431) = 679 - 862 = -183 kJ/mol. Since the result is negative, the reaction is exothermic.

Question 2: In an experiment, the bond energy of a certain molecule is found to be 150 kJ/mol. If 3 bonds of this type are broken and 2 bonds are formed during a reaction, what is the total energy change?

Answer: Total energy change = (3 × 150) - (2 × 150) = 450 - 300 = 150 kJ/mol. The reaction absorbs energy, so it is endothermic.

Question 1: Define an exothermic reaction and give one example from everyday life.

Answer: An exothermic reaction releases energy, usually as heat or light. Example: Combustion of gasoline in a car engine.

Question 2: Explain why bond energy calculations can help determine whether a reaction is exothermic or endothermic.

Answer: Because bond energy calculations show whether more energy is released when bonds form or needed to break bonds, indicating if the reaction releases or absorbs energy.

Question 1: List two safety precautions to consider when working with gases in bond energy experiments.

Answer: Use proper protective equipment such as gloves and goggles; work in a well-ventilated area or under a fume hood to avoid inhaling gases.

Question 2: Identify two variables that could affect the accuracy of bond energy measurements in a laboratory setting.

Answer: Temperature fluctuations and measurement precision of energy used or released.

Question 1: A chemical reaction releases 250 kJ/mol of energy. Is this reaction exothermic or endothermic? Justify your answer.

Answer: It is exothermic because the energy released is positive, indicating energy is given off during the reaction.

Question 2: Explain how bond energy calculations are used in the industry to develop new fuels or materials.

Answer: In industry, bond energy calculations help scientists predict the energy output or absorption of new fuels and materials. By understanding the strength of bonds, researchers can design compounds that release more energy in combustion or are more stable, leading to more efficient energy sources and safer materials.