Heat of reaction at constant volume is measured in which apparatus?

Which of the following is $NOT$ a state function?

Internal energy is

If a gas expands at constant temperature and pressure,then its:

Identify the type of system if boiling water is kept in a half-filled closed vessel.

Observe the following properties: Volume,enthalpy,density,temperature,heat capacity,pressure,internal energy. The number of extensive properties in the above list is