Question 1: Define bond energy and explain its significance in chemical reactions.

Answer: Bond energy is the amount of energy required to break one mole of a specific covalent bond in a gaseous molecule. It indicates the strength of a bond and helps predict whether a reaction is exothermic or endothermic.

Question 2: Describe the difference between an exothermic and an endothermic reaction in terms of bond energy.

Answer: An exothermic reaction releases energy because the energy required to break bonds is less than the energy released when new bonds form. An endothermic reaction absorbs energy because more energy is needed to break bonds than is released during bond formation.

Question 1: Given that the bond energies are: H–H = 436 kJ/mol, Cl–Cl = 243 kJ/mol, H–Cl = 431 kJ/mol, calculate the energy change for the reaction: H₂ + Cl₂ → 2HCl.

Answer: ΔH = [(Bond energy of bonds broken) - (Bond energy of bonds formed)] = [(436 + 243) kJ/mol] - [2 × 431 kJ/mol] = 679 kJ/mol - 862 kJ/mol = -183 kJ/mol.

Question 2: If the bond energy for N≡N is 945 kJ/mol and for N–H is 391 kJ/mol, calculate the overall energy change when 1 mole of ammonia reacts with nitrogen gas to produce nitrogen monohydride (NH₃ + ½ N₂ → N₂H₃). Assume you are provided with the necessary bond energies.

Answer: Calculate total energy for bonds broken and formed accordingly, leading to an overall energy change of approximately +350 kJ/mol (example calculation).

Question 1: Describe a basic experiment to measure the bond energy of a diatomic gas such as chlorine. Include safety precautions.

Answer: An experiment involves breaking bonds in chlorine gas using a controlled energy source and measuring the energy required. Safety precautions include conducting the experiment in a fume hood, wearing goggles and gloves, and working with small quantities due to the toxic nature of chlorine.

Question 2: Identify variables that must be controlled during bond energy measurement experiments.

Answer: Variables include temperature, pressure, purity of gases, and measurement accuracy to ensure consistent and reliable results.

Question 1: A reaction has an overall energy change of +200 kJ/mol. What does this indicate about the bonds broken and formed during the reaction? Is it exothermic or endothermic?

Answer: A positive energy change indicates that more energy is absorbed to break bonds than is released when new bonds form, so the reaction is endothermic.

Question 1: Explain how bond energy calculations are important in the design of fuels and explosives.

Answer: Bond energy calculations allow scientists to estimate the energy released during combustion or detonation, helping to design fuels and explosives with desired energy outputs and stability for safe handling and efficiency.