Experiment 1: Heat of neutralization (M.Sc, B.Sc) Important Practical viva questions and answers

Summary

This video focuses on key concepts related to calorimetry and thermochemistry, discussing practical questions for MSC and BSE exams. Topics include the enthalpy of neutralization, solution enthalpy, calorimeter constants, and exothermic/endothermic reactions. It explains the heat exchange processes, differences between calorimetry and colorimetry, and examines factors affecting enthalpy changes. Practical applications such as strong acid-base reactions and polybasic acids are highlighted, making it a useful guide for students preparing for chemistry practical exams.

Takeaways

• 📚 The heat of neutralization or enthalpy of neutralization is the enthalpy change when one gram equivalent of acid is neutralized by a base, typically around -57.3 kJ/mol for strong acids and bases.
• 🌡️ Enthalpy of solution refers to the enthalpy change when one mole of a substance is dissolved in a specific amount of solvent at a set temperature and pressure.
• 🧪 A thermometer calibrated to one-third degree precision is used in calorimetry to ensure more accurate results.
• ⚖️ The calorimeter constant is the ratio of enthalpy change (ΔH) to temperature change (ΔT), representing the heat capacity of the calorimeter.
• 💧 The water equivalent of a thermos flask is the amount of heat required to raise its temperature by 1°C.
• 🌍 Calorimetry measures heat changes in chemical reactions, while colorimetry is used to measure the concentration of colored solutions.
• 🧫 The enthalpy of neutralization for strong acids and bases is consistent, typically -57.3 kJ/mol, because of the complete ionization and consistent formation of water.
• 🔥 Exothermic reactions release heat, while endothermic reactions absorb heat during a chemical process.
• 🧪 A thermos flask represents an isolated system, meaning it doesn't exchange energy or matter with its surroundings.
• ⚛️ Polybasic acids can release multiple hydrogen ions per molecule, indicating their capacity to undergo several reactions.

Q & A

What is the enthalpy of neutralization?

The enthalpy of neutralization is the heat change when one gram equivalent of an acid is neutralized by a base, or vice versa. For strong acids and bases, it is approximately -57.3 kJ/mol.

What is the enthalpy of solution?

The enthalpy of solution refers to the heat change that occurs when one mole of a substance is dissolved in a specific number of moles of solvent at a particular temperature and pressure.

Why is a thermometer calibrated to one-third degree used in calorimetry?

A thermometer calibrated to one-third degree is used in calorimetry to achieve more accurate results in measuring temperature changes.

What is the meaning of the enthalpy of neutralization for strong acids and strong bases?

The enthalpy of neutralization for strong acids and bases is the heat released when one gram equivalent of a strong acid reacts with a strong base. The value is approximately -57.3 kJ/mol because it involves the formation of water from H+ and OH- ions.

What is a calorimeter constant?

The calorimeter constant, denoted as C Cal, quantifies the heat capacity of the calorimeter. It is the ratio of the enthalpy change (ΔH) to the temperature change (ΔT).

What is the water equivalent of a thermos flask?

The water equivalent of a thermos flask is the amount of heat required to raise the temperature of the thermos flask by 1°C.

What is the difference between calorimetry and colorimetry?

Calorimetry measures heat changes during chemical reactions, while colorimetry is used to determine the concentration of colored solutions by measuring absorbance.

Why is the enthalpy of neutralization for strong acids and strong bases always the same?

The enthalpy of neutralization for strong acids and bases is always about -57.3 kJ/mol because it involves the combination of H+ ions from the acid with OH- ions from the base, forming water molecules.

What is an exothermic reaction?

An exothermic reaction is a chemical reaction in which heat is released or evolved. An example is the neutralization reaction between HCl and NaOH.

What is a polybasic acid?

A polybasic acid can release more than one hydrogen ion (H+) per molecule during a reaction, meaning it has multiple ionizable hydrogen atoms.