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.

 

[DeeNos]

To answer this question, you need to understand the concept of oxidation and reduction. In a chemical reaction, oxidation is the process of losing electrons, while reduction is the process of gaining electrons. An oxidizing agent is a substance that causes another substance to undergo oxidation by accepting electrons itself.

In the given scenario, sulphuric acid (H2SO4) is acting as an oxidizing agent. This means that it is accepting electrons from the other substances in the reaction. In the reaction between H2SO4 and NaX (where X = Cl, Br, or I), the H2SO4 molecule is reduced to form H2O, while the NaX molecule is oxidized to form HX.

Now, to determine which sample(s) sulphuric acid is acting as an oxidizing agent, we need to look at the oxidation states of the elements involved. In NaX, the oxidation state of Na is +1 and the oxidation state of X is -1. In H2SO4, the oxidation state of H is +1 and the oxidation state of S is +6.

When H2SO4 reacts with NaCl, the oxidation state of Cl remains -1 in HCl, which is the product. This means that there is no change in the oxidation state of Cl, and therefore, sulphuric acid is not acting as an oxidizing agent in this reaction.

When H2SO4 reacts with NaBr, the oxidation state of Br increases from -1 to 0 in HBr, which is the product. This means that Br has undergone oxidation, and therefore, sulphuric acid is acting as an oxidizing agent in this reaction.

Similarly, when H2SO4 reacts with NaI, the oxidation state of I increases from -1 to 0 in HI, which is the product. This means that I has undergone oxidation, and therefore, sulphuric acid is also acting as an oxidizing agent in this reaction.

Therefore, the correct answer is C - sulphuric acid acts as an oxidizing agent in the reactions with sodium bromide and sodium iodide.