When a system absorbs $8 \ kJ$ of heat and does $2.2 \ kJ$ of work on the surroundings,calculate the internal energy change. (in $kJ$)

In a particular reaction, $4 \text{ kJ}$ of heat is released by the system and $12 \text{ kJ}$ of work is done on the system. Calculate the $\Delta H$ and $\Delta U$.

At the $1$ bar pressure,the volume of a gas is $0.6 \ L$. If the gas receives $122 \ J$ of heat at $1$ bar pressure,the volume becomes $2 \ L$. Calculate the change in its internal energy. $(1 \ L \cdot bar = 101.32 \ J)$

Consider the same expansion,but this time against a constant external pressure of $1 \ atm$.

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

Calculate the difference between $\Delta H$ and $\Delta U$ for the combustion of $n$-octane at $25^{\circ}C$. (in $kJ$)