Calculate the change in internal energy of the system if 20 kJ of work is done on the system and it releases 10 kJ of heat in a particular reaction.

What are the products formed when $\mathrm{Li}_2 \mathrm{CO}_3$ undergoes decomposition?

Identify the product formed from chlorobenzene on heating with conc. $\mathrm{HNO}_3$ in presence of conc. $\mathrm{H}_2 \mathrm{SO}_4$.

What are the respective oxidation states of sulphur atoms numbered 1 to 4 in tetrathionate ion shown below?