HSC Chemistry: Measure the enthalpy of Neutralisation| Module 6

Summary

This script discusses the principles of calorimetry, focusing on measuring the enthalpy change of reactions. It explains the setup of a typical calorimeter experiment, introduces the concept of specific heat capacity, and demonstrates how to calculate enthalpy change using the formula q = mcΔT. The video also covers molar enthalpy of neutralization, highlighting the standard value of -57 kJ/mol for strong acid-strong base reactions and noting that weaker acids or bases result in less energy release. Practical aspects, such as choosing the right base for neutralizing a sulfuric acid spill, are also addressed, emphasizing safety and the importance of minimizing heat loss in experiments.

Takeaways

• 🔍 Calorimetry is the process of determining the enthalpy change of a reaction by measuring the heat absorbed or released.
• 🧪 A calorimeter is an instrument used to measure the enthalpy change in a system, often involving a setup with an insulated cup and a thermometer.
• 🌡️ The temperature change during a reaction is a key measurement, which can be used to calculate the enthalpy change when combined with the mass of the substance and its specific heat capacity.
• ⚖️ The specific heat capacity (c) is the amount of energy required to raise the temperature of one gram of a substance by one degree Celsius or Kelvin, typically 4.18 J/g·K for water.
• 🔄 The enthalpy change (ΔH) is calculated using the formula ΔH = -q/n, where q is the heat exchanged and n is the number of moles of product formed.
• 💧 Molar enthalpy of neutralization is the heat change when one mole of water is formed in a neutralization reaction, typically around -57 kJ/mol for strong acid-strong base reactions.
• 🌡️ Lab conditions for measuring molar enthalpy of neutralization are standardized at 25 degrees Celsius and 100 kilopascals to ensure consistency.
• 🧩 In a neutralization reaction, all reactions go to completion regardless of the strength of the acid or base, but the enthalpy change can vary with the presence of weak acids or bases.
• 🚨 In chemical spills, using a weak base like sodium carbonate can be safer than a strong base due to less heat release and its ability to absorb the acid.
• 📝 The importance of significant figures in recording measurements and calculations cannot be overstated, as incorrect rounding can lead to significant errors in results.
• 🔍 The main source of error in calorimetry experiments is heat loss to the surroundings, which can be mitigated by using better insulation or heat shields.

Q & A

What is calorimetry?

Calorimetry is the process of determining the enthalpy of a reaction by measuring the heat absorbed or released during the reaction.

What is a calorimeter?

A calorimeter is an instrument used to measure the enthalpy change of a reaction by observing the temperature change of a known amount of substance.

What are the typical components of a calorimeter setup?

A typical calorimeter setup includes an insulated cup containing a known mass of water and a thermometer to measure the temperature change during a reaction.

How is the enthalpy change of a reaction calculated?

The enthalpy change of a reaction is calculated using the formula ΔH = -q/n, where q is the heat absorbed or released by the system and n is the number of moles of product formed.

What is q in the context of calorimetry?

In calorimetry, q represents the heat absorbed or released by the substance, which can be calculated using the formula q = mcΔT, where m is the mass of the substance, c is the specific heat capacity, and ΔT is the temperature change.

What is the specific heat capacity and why is it important in calorimetry?

The specific heat capacity is the amount of energy required to raise the temperature of one gram of a substance by one degree Celsius or one Kelvin. It is important in calorimetry because it is used to calculate the heat absorbed or released by the substance during a reaction.

What is the molar enthalpy of neutralization?

The molar enthalpy of neutralization is the enthalpy change in a neutralization reaction when exactly one mole of water is formed.

Why is the molar enthalpy of neutralization typically negative?

The molar enthalpy of neutralization is typically negative because neutralization reactions are exothermic, meaning they release heat.

What is the typical temperature and pressure for laboratory settings when measuring enthalpy changes?

The typical temperature and pressure for laboratory settings when measuring enthalpy changes are 25 degrees Celsius and 100 kilopascals, respectively.

Why would a weak base be preferred over a strong base when neutralizing a chemical spill, such as sulfuric acid?

A weak base would be preferred because it can absorb the liquid of the acid, limit the spread of the acid, and release less heat during the reaction, reducing the risk of additional dangers in a classroom setting.

What is the main source of error in a calorimetry experiment?

The main source of error in a calorimetry experiment is heat loss to the surroundings, which can result in a lower measured q value than in theory.

How can the experiment be improved to prevent heat loss?

The experiment can be improved by using double insulation, such as double-walled styrofoam cups, to minimize heat loss to the surroundings.