All nitrates decompose when heated. the extent to which a nitrate decomposes is determined by the metal in the salt.1) sodium nitrite is a reducing agent.- what would be observed if an excess of sodium nitrite solution was added to a solution of acidified potassium manganate (vii)? 2) copper(ii) nitrate decomposes to form copper(ii) oxide, nitrogen dioxide and oxygen. - what is the relationship between the extent of decomposition and the reactivity of the metal in the nitrate?