Termokimia (2) | Menentukan Perubahan Entalpi Reaksi berdasarkan Data Kalorimeter | Kimia kelas 11

Summary

This educational video explains how to determine the enthalpy change (ΔH) of chemical reactions using calorimetric data. It covers the fundamentals of calorimeters, which measure heat transfer during reactions, and provides formulas for calculating ΔH, such as ΔH = - (m * c * ΔT) / mol. The video demonstrates the method through examples of neutralization and combustion reactions. It also explains how to calculate moles of substances, apply the appropriate formula, and interpret results. The content is designed for those learning about thermochemistry and the practical use of calorimetry in determining enthalpy changes.

Takeaways

• 😀 A calorimeter is a device used to measure the heat released or absorbed during a chemical reaction, with the system being the reaction itself and the surroundings being the water and walls of the calorimeter.
• 😀 Exothermic reactions release heat, which is absorbed by the surroundings, including the water and walls of the calorimeter, in accordance with the first law of thermodynamics.
• 😀 The formula for calculating heat change (Q) is Q = mcΔT, where 'm' is the mass of the substance, 'c' is the specific heat capacity, and ΔT is the change in temperature.
• 😀 Enthalpy change (ΔH) for a reaction can be calculated using the formula ΔH = -m*c*ΔT/n, where 'n' is the number of moles involved in the reaction.
• 😀 If the heat capacity of the calorimeter is known, it can be incorporated into the enthalpy calculation using the formula ΔH = -m*c*ΔT + C*ΔT/n, where C represents the calorimeter's heat capacity.
• 😀 In the first example, the enthalpy change of the neutralization reaction between HCl and NaOH was calculated, with the mass of the solution derived from its volume and density.
• 😀 The amount of heat released during a neutralization reaction can be calculated by finding the molar amounts of the reactants involved (in this case, HCl and NaOH), using the volume and concentration given in the problem.
• 😀 In the second example, a similar approach was used to calculate the enthalpy change for the neutralization reaction between HNO3 and KOH, using the volume and molarity of the acid and base.
• 😀 In a bomb calorimeter, the change in temperature of the water is used to calculate the enthalpy change of combustion for a substance, such as methane.
• 😀 The enthalpy of combustion of methane was calculated using the heat change in the water, the heat capacity of the calorimeter, and the number of moles of methane burned during the reaction.

Q & A

What is the main focus of the video?

The video explains how to determine the enthalpy change (ΔH) of a reaction using calorimeter data.

What is a calorimeter, and how does it work?

A calorimeter is a device that contains a system and its surrounding environment. The system is the chemical reaction, and the surroundings are the water and the walls of the calorimeter. It measures the heat exchanged during a chemical reaction.

What types of reactions are typically studied using a calorimeter?

Calorimeters are often used to study exothermic reactions, which release heat during the process. The heat released by the reaction is absorbed by the surrounding water and walls of the calorimeter.

What is the formula for calculating the heat absorbed by the environment in a calorimeter?

The formula for calculating the heat absorbed is Q = mcΔT, where Q is the heat absorbed (in Joules), m is the mass of the substance (in grams), c is the specific heat capacity (in Joules per gram per degree Celsius), and ΔT is the change in temperature (in Celsius).

What does the negative sign in the formula for ΔH indicate?

The negative sign in the formula for ΔH indicates that the reaction is exothermic, meaning it releases heat to the surroundings.

How is the enthalpy change (ΔH) calculated if the calorimeter's heat capacity is known?

If the heat capacity of the calorimeter is known, the enthalpy change is calculated using the formula: ΔH = -mcΔT + CΔT/n, where C is the heat capacity of the calorimeter, n is the number of moles of reactants involved in the reaction, and other variables are as described previously.

What is the specific heat capacity of water, as used in the examples?

The specific heat capacity of water, as used in the examples, is 4.2 Joules per gram per Kelvin (J/g°C).

What is the formula used to calculate the enthalpy change of neutralization reactions?

For neutralization reactions, the enthalpy change is calculated using the formula: ΔH = -m × c × ΔT / n, where m is the mass of the solution, c is the specific heat capacity, ΔT is the temperature change, and n is the number of moles of the product (usually water in neutralization reactions).

What is the method to calculate moles of reactants involved in the reaction?

To calculate the moles of reactants, multiply the volume of the solution by its molarity. For example, if the volume of HCl is 50 mL and its concentration is 0.4 M, the number of moles is calculated as 50 mL × 0.4 M = 20 millimoles.

How do you convert moles from millimoles to moles when calculating enthalpy change?

To convert from millimoles to moles, divide by 1000. For example, 20 millimoles is converted to 0.020 moles by dividing by 1000.