Answer all the questions on halide ions as reducing agents and their reactions with concentrated sulfuric acid, then hit the check answers button and scroll down to get your score.
1. Which halide ion is the strongest reducing agent?
2. In the reaction 2Br− → Br2 + 2e−, bromide ions are being:
3. When a solid chloride (e.g. NaCl) reacts with concentrated H2SO4, the main gaseous product is:
4. In the reaction between NaCl(s) and concentrated H2SO4, the role of H2SO4 is mainly:
5. Write the formula of the acid that is formed when a fluoride (e.g. NaF) reacts with concentrated H2SO4:
6. Which equation best represents the acid-base step for bromide with concentrated sulfuric acid?
7. With bromide ions and concentrated H2SO4, some HBr is oxidised. One reduction product of sulfuric acid is:
8. In the oxidation step for bromide, HBr is oxidised to Br2. The oxidation state of bromine changes from:
9. When iodide ions react with concentrated H2SO4, sulfuric acid can be reduced beyond SO2. Which product is commonly seen?
10. What observation suggests iodine (I2) is formed in the reaction with iodide?
11. Give the formula of the “hydrogen halide” produced in the initial acid-base step when NaI reacts with concentrated H2SO4:
12. Which halide shows little or no redox reaction with concentrated H2SO4 (mainly acid-base only)?
13. In the reaction 2HBr + H2SO4 → Br2 + SO2 + 2H2O, the oxidising agent is:
14. Put these halide ions in order of increasing reducing power (weakest → strongest): Cl−, Br−, I−
15. Which statement best explains why I− is a stronger reducing agent than Cl−?
16. Which gas is responsible for “steamy fumes” when chloride reacts with concentrated sulfuric acid?
17. A common observation with bromide + concentrated H2SO4 is orange/brown fumes. These are mainly:
18. Give the formula of the sulfur-containing gas produced when H2SO4 is reduced to sulfur dioxide:
19. In the reaction between iodide and concentrated H2SO4, which product can cause a “rotten egg” smell?
20. Which overall trend is correct for the ease of oxidation of halide ions (easiest → hardest)?
