Thermodynamics ...

To which portion of the heating curve for water does $$C=1.00 \ cal/{g}^{o}C$$ apply?

For a thermodynamics process to be reversible, the temperature difference between hot body and the working substance should be 

In a thermodynamic process, a system absorbs 2 k cal of heat and at the same time does 800 J of work. The change in internal energy of the system is

The criterion for a spontaneous process is :

Consider the following changes
$$M\left( s \right) \longrightarrow M\left( g \right) $$     ...(1)
$$M\left( g \right) \longrightarrow { M }^{ 2+ }\left( g \right) +2{ e }^{ - }$$     ....(2)
$$M\left( g \right) \longrightarrow { M }^{ + }\left( g \right) +{ e }^{ - }$$     ....(3)
$${ M }^{ + }\left( g \right) \longrightarrow { M }^{ 2+ }\left( g \right) +{ e }^{ - }$$    ...(4)
$$M\left( g \right) \longrightarrow { M }^{ 2+ }\left( g \right) +2{ e }^{ - }$$    ...(5)
The second ionisation energy of $$M$$ could be determined from the energy values associated with:

In which of the processes, does the internal energy of the system remain constant?

Thermodynamic condition for irreversible spontaneous process at constant '$$T$$' and '$$P$$' is:

For the reaction $$N_2+3X_2 \rightarrow 2NX_3$$ where $$X = F, Cl$$ (the average bond energies are $$F-F = 155 \ kJ \ mol^{-1}$$, $$N-F = 272 \  kJ \ mol^{-1}$$, $$Cl-Cl=242\ kJ \ mol^{-1}$$ , $$N-Cl=200\  kJ \ mol^{-1}$$ and $$N \equiv N = 941 kJ\, mol^{-1}$$). The heats of formation of $$NF_3$$ and $$NCl_3$$ in $$kJ\ mol^{-1}$$, respectively, are closest to:

The molar enthalpy change for $$H_2O(1)\rightleftharpoons H2O(g)$$ at $$373$$K and $$1$$ atm is $$41$$kJ/mol. Assuming ideal behavior, the internal energy change for vaporization of $$1$$ mol of water at $$373$$K and $$1$$ atm in kJ $$mol^{-1}$$ is $$?$$

Under which of the following conditions is the relation, 
$$\Delta H=\Delta U+P\Delta V$$ valid for closed system?