18 Questions
What is the correct definition of internal energy of a system?
It is the sum of the kinetic energy and potential energy of all its components.
Which of the following quantities is NOT involved in enthalpy?
Pressure
What is the best description of enthalpy?
A thermodynamic quantity that measures the energy changes in a chemical reaction.
Which of the following pairs of descriptions differentiates endothermic and exothermic reactions?
Endothermic : absorbs energy ; Exothermic : releases energy
What is the primary difference between internal energy and enthalpy?
Internal energy is a path function, while enthalpy is a state function.
Which of the following statements about energy transformations is TRUE?
Energy can be transformed from one form to another in a chemical reaction.
What is the definition of enthalpy in a system?
The sum of its internal energy plus the product of its pressure and volume
What type of function is enthalpy?
A state function
What happens to the enthalpy of a system when heat flows from the system to its surroundings?
The enthalpy of the system decreases
What is the purpose of using enthalpy in chemical reactions?
To measure the energy changes that occur in the reaction
What is the change in enthalpy represented by?
ΔH = Hfinal - Hinitial
What is the type of reaction when the enthalpy of a reaction is positive?
Endothermic reaction
What is the enthalpy change that accompanies the melting of 1 mol of a substance?
Enthalpy of fusion
What is the internal energy of a system?
The sum of the kinetic energy and potential energy of all its components
Which of the following is a state function?
All of the above
What is the correct definition of a change in enthalpy?
ΔH = Hfinal – Hinitial
What is the main difference between enthalpy and enthalpy of a reaction?
Enthalpy is the change in energy that happens in a chemical reaction, while enthalpy of a reaction is the difference in enthalpy between products and reactants
What is the relation between enthalpy and internal energy?
Enthalpy is the sum of internal energy and pressure
Study Notes
Understanding Enthalpy
- Enthalpy is a thermodynamic quantity used to measure energy changes in chemical reactions.
- It is defined as the sum of internal energy (U) and the product of pressure (P) and volume (V): H = U + PV.
- Enthalpy is a state function, meaning it only depends on the current state of a system and not on how it got there.
Internal Energy vs. Enthalpy
- Internal energy is the sum of kinetic energy (KE) and potential energy (PE) of all components in a system.
- Internal energy is related to enthalpy, but they are not the same thing.
Measuring Enthalpy Changes
- Enthalpy changes (ΔH) are measured in chemical reactions, and can be positive or negative.
- A negative enthalpy change indicates an exothermic reaction, where heat flows from the system to the surroundings.
- A positive enthalpy change indicates an endothermic reaction, where heat flows from the surroundings to the system.
Types of Enthalpy Changes
- The enthalpy change that accompanies the melting (fusion) of 1 mol of a substance is a specific type of enthalpy change.
- The enthalpy change that accompanies the vaporization of 1 mol of a substance is another specific type of enthalpy change.
Key Concepts
- Enthalpy is a state function, and changes in enthalpy can be measured in chemical reactions.
- Enthalpy is not the same as internal energy, but they are related.
- Enthalpy changes can be positive or negative, indicating endothermic or exothermic reactions.
Test your knowledge on enthalpy in the context of chemical reactions. This quiz is designed for Grade 12 learners and covers the basics of enthalpy in General Chemistry 2.
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