Answer: The oxidizing agent in the given reaction will be NO3 -1 ion.
Reactant side:
Oxidation state of hydrogen = +1
Oxidation state of oxygen = -2
Oxidation state of Tin = 0
Oxidation state of chlorine = -1
Oxidation state of nitrogen = +5
Product side:
Oxidation state of hydrogen = +1
Oxidation state of oxygen = -2
Oxidation state of Tin = +6
Oxidation state of chlorine = -1
Oxidation state of nitrogen = +4