With which sample(s) of halide does sulphuric acid act as an oxidising agent?

[mutineer123]

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?

 

[jd12345]

It only oxidises Br- and I- to Br2 and I2 so C.) sodium bromide and sodium iodide should be the correct option

 

[chemisttree]

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?

http://www.chemguide.co.uk/inorganic/group7/halideions.html

 

[mutineer123]

http://www.chemguide.co.uk/inorganic/group7/halideions.html

Thank you! awesome site.