Enthalpy (H) is the sum of internal energy (U) and product of pressure and volume (PV). It is given by the equation-
H=U+PV
Question 1: What does U represent in the enthalpy equation?
(a) Volume
(b) Internal energy
(c) Free energy
(d) Potential energy
Answer: (b)
Explanation: In thermodynamics, Internal energy U is the total energy E of the system.
Question 2: How do we represent change in enthalpy?
(a) ΔH
(b) ΔU
(c) ΔV
(d) ΔE
Answer: (a)
Explanation: The heat content of a system at constant pressure is called enthalpy (H).
Question 3: The enthalpy of a substance (denoted by H), is defined as
(a) H = U - PV
(b) H = U + PV
(c) H =-U + PV
(d) H =-U - PV
Answer: (b)
Explanation: The sum of internal energy (U) and the product of pressure and volume is enthalpy, represented by equation-
H = U + PV
Question 4: SI units of enthalpy are
(a) Kelvin
(b) Candela
(c) Joules
(d) Newtons
Answer: (c)
Explanation: The joule is the SI unit of enthalpy. The equation H=U+PV can be used to express enthalpy.
Question 5: What does PV represent in the enthalpy equation?
(a) Product of potential energy and volume
(b) Product of pressure and internal energy
(c) Product of force and enthalpy
(d) Product of pressure and volume
Answer: (d)
Explanation: In the enthalpy equation, H = U + PV
P represents pressure and V represents volume.
Question 6: For an ideal gas, enthalpy equation becomes-
(a) H = U - RT
(b) H =-U - RT
(c) H =-U + RT
(d) H = U + RT
Answer: (d)
Explanation: We know for an ideal gas PV = RT.
Question 7: In enthalpy equation, ΔU represents -
(a) Change in enthalpy
(b) Change in internal energy
(c) Change in potential energy
(d) Change in volume
Answer: (b)
Explanation: In thermodynamics, Internal energy U is the total energy E of the system.
Question 8: Which of the following statements about the enthalpy equation is true?
(a) The Internal energy is represented by H
(b) The Change in enthalpy is denoted by ΔE
(c) The internal energy and enthalpy has same units
(d) PV is the product of potential energy and volume
Answer: (c)
Explanation: H=U+PV is the equation for enthalpy. The conventional units for pressure and volume are the pascal or kilogramme per metre per second-squared and meter-cubed respectively.
Question 9: kg.m^2/s^2 are the units of-
(a) P
(b) U
(c) V
(d) None of these
Answer: (b)
Explanation: H=U+PV is the equation for enthalpy.
Question 10: Total enthalpy of a system is given by-
(a) m/H
(b) H/m
(c) mH
(d) None of the above
Answer: (c)
Explanation: Total enthalpy of a system is given by formula mH.
Take Enthalpy Equation Homework Help Today!
Enthalpy (H) is the sum of internal energy (U) and product of pressure and volume (PV). It is given by the equation-
H=U+PV
Change in enthalpy between initial and final state is given as-
ΔH = ΔU + ΔPV
Enthalpy is given by the equation H=U+PV. Standard units of pressure are pascal or kilogram per meter per second-squared (Kg/m2) and the standard unit for volume is meter-cubed m3. The product of these two units is kilogram meter-squared per second-squared Kg.m2/s2 This is also known as a joule. Joule is also a unit of internal energy U.
Therefore, unit for enthalpy is the sum of these two units, joule.
The SI unit of enthalpy is joule. Enthalpy can be expressed by equation-
H=U+PV
Here, U is internal energy, P is pressure and V is volume.
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