Question

Which of the following statements is incorrect about enthalpy?

• A. Its absolute value can be determined accurately.
• B. It is a state function.
• C. It is an extensive property.
• D. Enthalpy change can be determined using the first law of thermodynamics.

Hint:

Remember, absolute enthalpy values are not measurable. Only changes in enthalpy (ΔH) during a process have thermodynamic significance.

Answer 1

The Correct Option is A

Step 1: Understand what enthalpy is.
Enthalpy is a thermodynamic state function defined as: \[ H = U + PV \] However, only changes in enthalpy (\(\Delta H\)) can be measured, not the absolute value. Step 2: Evaluate each option. \begin{itemize} \item Option (1) is incorrect because the absolute value of enthalpy cannot be measured—only enthalpy changes are meaningful. \item Option (2) is correct: Enthalpy is a state function. \item Option (3) is correct: Enthalpy depends on the amount of substance, so it is extensive. \item Option (4) is correct: Enthalpy change relates to heat change under constant pressure, which is derived using the first law of thermodynamics. \end{itemize}