3. Which ion(s) precipitate upon addition of the weakly basic ammonia solution?

Question

3. Which ion(s) precipitate upon addition of the weakly basic ammonia solution? 4. In this experiment, the choice of precipitating reagent is important. Briefly explain what the consequences would be if excess 6M NaOH solution instead of 6 M NH3 solution were used to separate Fe" and Al-ions from the remaining ions at pH 9-10. Include appropriate chemical equations to support your conclusions. 5. In Part II of the procedure, you created a buffer system by first neutralizing the supernatant solution containing all the ions with 6 M NHs solution. Explain what forms of NHs were present in the final solution and how they could function as a buffer. Analysis of Cations 11

Explanation / Answer

Q4.

Aqueous NH3 reacts with Fe3+ to produce red brown Fe(OH)3.

Fe3+ (Aqueous) + 3NH3(Aqueous) + 3H2O(Liquid) Fe(OH)3(Solid)    + 3NH4+ [The Precipitate is not soluble in Aqueous NH3

Fe3+ (Aqueous) + 3OH-(Aqueous) Fe(OH)3(Solid)    [The precipitate will not be dissolved in Excess NaOH]

Aqueous NH3 reacts with Al3+ to produce a white gelatinous precipitate of Al(OH)3.

Al3+ (Aqueous) + 3NH3(Aqueous) + 3H2O(Liquid) Al(OH)3(Solid)    + 3NH4+ [The Precipitate is amphoteric in nature and the precipitate is not soluble in Excess aqueous Ammonia ]

Al3+ (Aqueous) + 3OH-(Aqueous) Al(OH)3(Solid)    [If we add excess NaOH to the precipitate, it will form complex ion [Al(OH)4]- ]

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.