Starch-iodide paper is used for the test of:

Potassium dichromate acts as a strong oxidizing agent in acidic solution. During this process,the oxidation state of chromium changes from

In the following reaction,which substance acts as a reducing agent?
$14H^+ + Cr_2O_7^{2-} + 3Ni \to 2Cr^{3+} + 7H_2O + 3Ni^{2+}$

What happens when sulphur dioxide is passed through an aqueous solution of $Fe(III)$ salt?

Consider the reactions:
$(a)$ $H_3PO_{2(aq)} + 4AgNO_{3(aq)} + 2H_2O_{(l)} \to H_3PO_{4(aq)} + 4Ag_{(s)} + 4HNO_{3(aq)}$
$(b)$ $H_3PO_{2(aq)} + 2CuSO_{4(aq)} + 2H_2O_{(l)} \to H_3PO_{4(aq)} + 2Cu_{(s)} + H_2SO_{4(aq)}$
$(c)$ $C_6H_5CHO_{(l)} + 2[Ag(NH_3)_2]^+_{(aq)} + 3OH^-_{(aq)} \to C_6H_5COO^-_{(aq)} + 2Ag_{(s)} + 4NH_{3(aq)} + 2H_2O_{(l)}$
$(d)$ $C_6H_5CHO_{(l)} + 2Cu^{2+}_{(aq)} + 5OH^-_{(aq)} \to$ No change observed.
What inference do you draw about the behaviour of $Ag^+$ and $Cu^{2+}$ from these reactions?

For the given reaction,which of the following is not used to change the colour of the solution from orange to green?
$K_2Cr_2O_7 / H^{+} + y \to Cr^{+3} + \text{Others}$
$(\text{orange}) \quad \quad \quad (\text{green})$