In the reaction $C + H_2O \to CO + H_2$,$H_2O$ acts as:

Which of the following is not a reducing agent?

When heated in air,brown copper powder turns black. This black powder would turn brown again when heated with:

Starch iodide paper is used to test for the presence of .........

Which of the following sets includes all the species that will change the orange colour of $K_2Cr_2O_7$ in acidic medium?

Identify the change in the oxidation state of the oxidising agent in the following redox reaction: $3H_3AsO_3(aq) + BrO_3^-(aq) \rightarrow Br^-(aq) + 3H_3AsO_4(aq)$