For an isochoric process,the first law of thermodynamics can be expressed as:

During the melting of an ice slab at $273 \ K$ and $1 \ atm$ pressure:

Two vessels $A$ and $B$ are connected via a stopcock. Vessel $A$ is filled with a gas at a certain pressure. The entire assembly is immersed in water and allowed to reach thermal equilibrium. After opening the stopcock,the gas from vessel $A$ expands into vessel $B$,and no change in temperature is observed. Which of the following statements is true?

When a system is supplied with $60 \ J$ of heat,it performs $15 \ J$ of work. The change in the internal energy of the system is ......... $J$.

If $\Delta H$ is the change in enthalpy and $\Delta E$ is the change in internal energy accompanying a gaseous reaction,which of the following is true?

$A$ gaseous sample expands from $200 \, cm^3$ to $500 \, cm^3$ against a constant external pressure of $750 \, torr$ while absorbing $1.5 \, J$ of heat. What is the change in internal energy of the system in $J$? $(1 \, atm \cdot L = 101.3 \, J)$