29 An iron nail is heated with concentrated sulphuric acid. Which of the following combinations is correct?
Gas given off
Color of solution formed
why is D but not C
fe2+ PALE GREEN= =
- N70Lv 71 十年前最愛解答
Because hot concentrated sulphuric acid is an OXIDIZING AGENT. Thus Iron will be oxidized to Fe3+ ions while sulphuric acid will be reduced to SO2:
2Fe (s) + 6H2SO4 (aq) → Fe2(SO4)3 (aq) + 6H2O (l) + 3SO2 (g)
Hence D is correct.
Pale green solution would be formed when Iron reacts with acids to give Fe2+ ions, e.g. when reacting with DILUTE H2SO4:
Fe (s) + H2SO4 (aq) → Fe2SO4 (aq) + H2 (g)
But in such case, Hydrogen, instead of SO2 would be given out. So C cannot be correct.
Please remember that reactions between H2SO4 & metal will give out:
- SO2 when H2SO4 acts as an oxidizing agent
- H2 when H2SO4 acts as an acid