Answer : The name of positive ion present in this sample is, hydronium ion.
Explanation :
For formation of a neutral ionic compound, the charges on cation and anion must be balanced.
The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Ion : An ion is formed when an atom looses or gains electron.
When an atom looses electrons, it will form a positive ion known as cation.
When an atom gains electrons, it will form a negative ion known as anion.
As per question, hydronium ion or hydrogen ion is having an oxidation state of +1 called as or
cation and nitrate ion
is an anion with oxidation state of -1.
Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral .
Hence, the name of positive ion present in this sample is, hydronium ion.