A black compound of manganese reacts with a halogen acid to give greenish yellow gas. When excess of this gas reacts with NH3 an unstable trihalide is formed. In this process the oxidation state of nitrogen changes from _________.
(i) – 3 to +3 (ii) – 3 to 0 (iii) – 3 to +5 (iv) 0 to – 3
