This question is about sodium halides - AQA - A-Level Chemistry - Question 9 - 2020 - Paper 1

The reaction produces steamy or white fumes of hydrogen chloride gas.

The equation for the reaction is: $2NaCl + H_2SO_4 \rightarrow Na_2SO_4 + HCl \uparrow$

Chloride ions act as a base or proton acceptor during the reaction.

The equation for the redox reaction is: $2NaBr + 2H_2SO_4 \rightarrow \\ Na_2SO_4 + Br_2 + SO_2 + 2H_2O$

In the reaction, bromide ions (Br$^{-}$) change oxidation state from -1 to 0 when forming bromine (Br$_2$), and sulfur changes oxidation state from +6 (in H$_2$SO$_4$) to +4 (in SO$_2$). Thus, Br is oxidized and H$_2$SO$_4$ is reduced, indicating a redox reaction.

A yellow or orange solution is observed due to the formation of bromine.

The ionic equation for the reaction is: $Cl_2 + 2Br^- \rightarrow 2Cl^- + Br_2$