Which of the following statements is incorrect?
Show Hint
- \(\mathrm{Fe^{2+}}\) ion also gives blood red colour with \(\mathrm{SCN^-}\) ion.
- \(\mathrm{Fe^{3+}}\) ion also gives blood red colour with \(\mathrm{SCN^-}\) ion.
- On passing \(\mathrm{H_2S}\) into \(\mathrm{Na_2ZnO_2}\) solution a white ppt of \(\mathrm{ZnS}\) is formed.
- Cupric ion reacts with excess of ammonia solution to give deep blue colour of \(\mathrm{[Cu(NH_3)_4]^{2+}}\) ion.
The Correct Option is A
Solution and Explanation
(1) \(\mathrm{Fe^{2+}}\) does not give the blood-red colour with \(\mathrm{SCN^-}\); the colour appears only after it is oxidised to \(\mathrm{Fe^{3+}}\). So the statement is incorrect.
(2) \(\mathrm{Fe^{3+} + SCN^- \rightarrow [Fe(SCN)]^{2+}}\) is blood red. Correct.
(3) Zincate \(\mathrm{Na_2ZnO_2}\) with \(\mathrm{H_2S}\) in alkaline medium gives white \(\mathrm{ZnS}\). Correct.
(4) \(\mathrm{Cu^{2+}}\) with excess \(\mathrm{NH_3}\) gives deep blue \(\mathrm{[Cu(NH_3)_4]^{2+}}\). Correct.
Hence statement (1) is the incorrect one.
Answer: (1) Fe2+ ion also gives blood red colour with SCN- ion.
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