$1.8 \ g$ of water is vaporized by supplying $4 \ kJ$ of heat at $100^{\circ}C$. What is the molar heat of vaporization of water at the same temperature?

$1 \, mol$ of oxygen gas is heated at constant volume from $20 \, ^oC$ to $30 \, ^oC$. What will be the change in the internal energy of the gas? Given the molar heat capacity of oxygen at constant pressure,$C_P = 7.03 \, cal \, mol^{-1} \, K^{-1}$ and $R = 2 \, cal \, mol^{-1} \, K^{-1}$. (Answer in $cal$)

The enthalpy of dilution of $4 \ M \ HCl$ to $2 \ M \ HCl$ is $-2.5 \ kJ/mol$. Find the enthalpy change when $500 \ mL$ of $4 \ M \ HCl$ is diluted to $2 \ M \ HCl$ (in $kJ$).

The enthalpy change for the reaction of $50.00 \ mL$ of ethylene with $50.00 \ mL$ of $H_2$ at $1.5 \ atm$ pressure is $\Delta H = -0.31 \ kJ$. The value of $\Delta E$ will be (in $kJ$)

Arrange the following in order of magnitude of work done by the system / on the system at constant temperature:
$(a)$ $|w_{reversible}|$ for expansion in infinite stage.
$(b)$ $|w_{irreversible}|$ for expansion in single stage.
$(c)$ $|w_{reversible}|$ for compression in infinite stage.
$(d)$ $|w_{irreversible}|$ for compression in single stage.
Choose the correct answer from the options given below:

An ideal gas is expanded from $(p_1, V_1, T_1)$ to $(p_2, V_2, T_2)$ under different conditions. The correct statement$(s)$ among the following is(are):
[$A$] The work done on the gas is maximum when it is compressed irreversibly from $(p_2, V_2)$ to $(p_1, V_1)$ against constant pressure $p_1$.
[$B$] The work done by the gas is less when it is expanded reversibly from $V_1$ to $V_2$ under adiabatic conditions as compared to that when expanded reversibly from $V_1$ to $V_2$ under isothermal conditions.
[$C$] The change in internal energy of the gas is $(i)$ zero,if it is expanded reversibly with $T_1=T_2$,and $(ii)$ positive,if it is expanded reversibly under adiabatic conditions with $T_1 \neq T_2$.
[$D$] If the expansion is carried out freely,it is simultaneously both isothermal as well as adiabatic.