Answer:- 
Explanations:- Transition elements shows variable oxidation states. So, while naming these compounds we use the roman numerals to tell their oxidation states.
For example, if someone writes just Iron oxide then it would not be correct since Iron could be in +2 or +3 states. So, it might be or 
. So, the right was is to mention the oxidation state of the transition metal.
If the name is written as Iron(II) in a compound then it means there is +2 charge on iron and it is .
The least amount of energy required to activate atoms or molecules to a state in which they can undergo a chemical reaction.
Answer:
(<em>i) Concentrated HNO3 can be stored and transported in aluminium containers as it reacts with aluminium to form a thin protective oxide layer on the aluminium surface. This oxide layer renders aluminium passive. (ii) Sodium hydroxide and aluminium react to form sodium tetrahydroxoaluminate(III) and hydrogen gas.</em>
