Concentrated sulphuric acid is added to separate solid samples of sodium chloride, sodium bromide or sodium iodide. With which sample(s) does sulphuric acid act as an oxidising agent? A sodium chloride only B sodium chloride and sodium bromide C sodium bromide and sodium iodide D sodium iodide only The answer is C. But what is the explanation? How do I approach questions like these, because I have no clue how to find the answer. I tried writing an equation for the 3 reaction, and they are all the same! NaX + H2SO4 --> NaHSO4 + HX ( You can also use the Na2SO4 reaction) So what thread do I follow to crack this?