Q1. What does the term 'enthalpy' (H) represent? (2019)
Solution:
Enthalpy (H) represents the total heat content of a system at constant pressure and is defined as internal energy plus pressure-volume work.
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Q2. Which of the following processes has a positive change in entropy? (2023)
Solution:
The melting of ice has a positive change in entropy as the solid structure becomes more disordered in the liquid state.
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Q3. In thermodynamics, the term 'enthalpy' is defined as: (2022)
Solution:
Enthalpy is defined as the heat content of a system at constant pressure, represented as H = U + PV.
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Q4. In thermodynamics, the term 'adiabatic' refers to a process that: (2019)
Solution:
An adiabatic process is one in which no heat is transferred to or from the system, meaning it occurs without heat exchange.
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Q5. The heat capacity at constant volume (Cv) for an ideal gas is related to which of the following? (2023)
Solution:
The heat capacity at constant volume (Cv) is directly related to the change in internal energy of the system.
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Q6. The heat capacity of a substance is defined as: (2023)
Solution:
The heat capacity of a substance is defined as the amount of heat required to raise the temperature of one mole of the substance by one degree Celsius.
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Q7. What is the standard enthalpy change (ΔH°) for the formation of water from its elements? (2022)
Solution:
The standard enthalpy change for the formation of water from its elements (H2 and O2) is -285.83 kJ/mol.
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Q8. What is the change in internal energy (ΔU) for an ideal gas undergoing an isothermal process? (2021)
Solution:
In an isothermal process for an ideal gas, the temperature remains constant, which means the internal energy does not change. Therefore, ΔU = 0.
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Q9. Which of the following processes increases the entropy of the system? (2022)
Solution:
The melting of ice increases the entropy of the system as it transitions from a solid to a liquid state, which has more disorder.
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Q10. Which of the following is NOT a characteristic of an exothermic reaction? (2019)
Solution:
An exothermic reaction releases heat and has a negative ΔH. It causes the temperature of the surroundings to increase, not absorb energy.
