Answer:
1) HNO3/H2SO4, 2) CH3CH2CH2Cl/AlCl3
Explanation:
Benzene is a stable aromatic compound hence it undergoes substitution rather than addition reaction.
When benzene undergoes substitution reaction, the substituent introduced into the ring determines the position of the incoming electrophile.
If I want to synthesize m-nitropropylbenzene, I will first carry out the nitration of benzene using HNO3/H2SO4 since the -nitro group is a meta director. This is now followed by Friedel Craft's alkykation using CH3CH2CH2Cl/AlCl3.
Answer 1)

+

----> 2 HCl
This is a pure
chemical reaction that is taking place.
In this reaction the two chemical species which are Chlorine and Hydrogen undergo addition reaction and form two moles of hydrochloric acid. No new species is formed except the combination of reactants which gives the product.
Answer 2) H + H ----> He + n
This is a nuclear reaction.
As the reactant species is undergoing a reaction which is resulting in formation of new species completely different than the elements in reactants.
Also there is a neutron which is generated after the reaction this is clear indication of nuclear fusion reaction. Hence, it can be called as nuclear reaction.
Answer:
5 million million atoms can fit at the end of a needle