When an anhydrous sodium halide, NaX\text{NaX}NaX, reacts with concentrated sulfuric acid, a toxic gas with a characteristic rotten egg smell is evolved along with other products.
Which option correctly identifies the halide ion, X−\text{X}^-X−, and the change in the oxidation state of sulfur during the redox reaction that produces this specific gas?
Halide ion: Br−\text{Br}^-Br−; change in sulfur oxidation state: +6→+4+6 \rightarrow +4+6→+4
Halide ion: I−\text{I}^-I−; change in sulfur oxidation state: +6→−2+6 \rightarrow -2+6→−2
Halide ion: I−\text{I}^-I−; change in sulfur oxidation state: +6→0+6 \rightarrow 0+6→0
Halide ion: Br−\text{Br}^-Br−; change in sulfur oxidation state: +6→−2+6 \rightarrow -2+6→−2
Practise Edexcel GCSE Chemistry Group 7 with exam-style questions for Foundation and Higher tier. 87 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.