An exothermic reaction is one which

For the isothermal reversible expansion of an ideal gas,which of the following is correct?

Fill in the blanks:
$(i)$ $A$ system that allows the exchange of energy but not matter with the surroundings is called a ........ .
$(ii)$ The total amount of energy consisting of the internal energy of a substance plus the product of its pressure and volume is called ........ .
$(iii)$ The change in energy that occurs when a chemical reaction is carried out at constant pressure is called ........ .

Which of the following is an intensive property?

An ideal gas undergoes isothermal expansion at constant pressure. During the process

The work done during reversible isothermal expansion of one mole of hydrogen gas at $25^{\circ}C$ from a pressure of $20 \ atm$ to $10 \ atm$ is
(Given $R = 2.0 \ cal \ K^{-1} \ mol^{-1}$)