Question

Which of the following assumptions appears reasonable for the isothermal process? H20 (liq, 1 bar) → H2O (liq, 1300 bar), T = 20°C. A. AU = 0, AH 0 B. AU = 0, AH 0 C. AU #0, AH = 0 D. None of the above Hinn nf diethyl ether using the Chen's rule is

Answer 1

Answer : The assumptions appears reasonable for the isothermal process is, $\Delta U=0$ and $\Delta H=0$

Explanation :

First law of thermodynamic : It states that the energy can not be created or destroyed, it can only change or transfer from one state to another state.

As per first law of thermodynamic,

$\Delta U=q+w$

The expression for internal energy is:

$\Delta U=nC_vdt$

The expression for enthalpy is:

$\Delta H=nC_pdt$

where,

$\Delta U$ = internal energy

q = heat

w = work done

n = number of moles

$C_v$ = specific heat capacity at constant volume

$C_p$ = specific heat capacity at constant pressure

$dt$ = change in temperature

As we know that, the term internal energy and enthalpy is the depend on the temperature and the process is isothermal that means at constant temperature.

T = constant

$\dt$ = 0

So, at constant temperature the internal energy and enthalpy is equal to zero. That means,

$\Delta U=0$ and $\Delta H=0$