In the neutral or faintly alkaline medium,$KMnO_4$ oxidises iodide into iodate. The change in oxidation state of manganese in this reaction is from?

After balancing the reaction $Cu + HNO_3 \rightarrow Cu(NO_3)_2 + NO_2 + H_2O$ in an acidic medium,the number of nitrogen atoms,the number of water molecules,and the net charge on the product side are respectively:

Aqueous solutions of hydrogen sulphide and sulphur dioxide when mixed together,yield

Assign $A, B, C, D$ from the given type of reaction for the following chemical equation:
$N_2 + 3H_2 \longrightarrow 2NH_3$

Assertion : When a metal is treated with conc. $HNO_3$,it generally yields a nitrate,$NO_2$,and $H_2O$.
Reason : Conc. $HNO_3$ reacts with a metal and first produces a metal nitrate and nascent hydrogen. The nascent hydrogen then further reduces $HNO_3$ to $NO_2$.

Write the net ionic equation for the reaction of potassium dichromate$(VI)$,$K_{2}Cr_{2}O_{7}$ with sodium sulphite,$Na_{2}SO_{3}$ in an acidic solution to give chromium$(III)$ ion and the sulphate ion.