A yellow-colored complex P upon addition of aqueous HNO3 forms a very pale violet-colored complex Q. Complex Q on reaction with NaCl forms a yellow-colored complex R. The species P, Q and R, respectively, that are consistent with the above observations, are
P = [Fe(H2O)5(OH)2+; Q = [Fe(H2O)6]3+ and R = [Fe(H2O)5(Cl)]2+
Identifying Complex P, Q, and R
The question asks us to identify three iron complexes, P, Q, and R, based on their colors and reactions with specific reagents. We are given the color of P (yellow), the color of Q (pale violet), and the color of R (yellow), along with the reactions that transform P into Q and Q into R.
Complex P: The Starting Yellow Complex
Complex P is described as yellow. We need to look at the options and see which complex is likely to be yellow. The first option suggests P is \( \text{[Fe(H}_2\text{O)}_5\text{(OH)]}^{2+} \). Iron(III) hydrolysis products, like \( \text{[Fe(H}_2\text{O)}_5\text{(OH)]}^{2+} \), are often yellow or brownish in aqueous solution due to charge transfer transitions.
Reaction 1: P to Q upon addition of HNO₃
Complex P reacts with aqueous HNO₃ (an acid) to form a very pale violet-colored complex Q. Let's consider the proposed structure of P from option 1, \( \text{[Fe(H}_2\text{O)}_5\text{(OH)]}^{2+} \). This complex contains a hydroxide ligand \( \text{(OH)}^- \). Adding an acid \( \text{(H}^+ \text{ from HNO}_3\text{)} \) will protonate the hydroxide ligand, turning it into a water molecule \( \text{(H}_2\text{O)} \).
The reaction would be:
| \( \text{[Fe(H}_2\text{O)}_5\text{(OH)]}^{2+}\text{(aq)} \) | \( + \text{ H}^+\text{(aq)} \) | \( \longrightarrow \) | \( \text{[Fe(H}_2\text{O)}_6\text{]}^{3+}\text{(aq)} \) |
| (Complex P) | (from HNO₃) | (Complex Q) |
The proposed complex Q in option 1 is \( \text{[Fe(H}_2\text{O)}_6\text{]}^{3+} \). This reaction transforms the \( \text{[Fe(H}_2\text{O)}_5\text{(OH)]}^{2+} \) complex into the hexaaquairon(III) ion, \( \text{[Fe(H}_2\text{O)}_6\text{]}^{3+} \). The hexaaquairon(III) ion is typically pale violet or almost colorless in dilute solutions. This matches the observed color change from yellow (P) to pale violet (Q).
Reaction 2: Q to R upon reaction with NaCl
Complex Q reacts with NaCl to form a yellow-colored complex R. NaCl provides chloride ions \( \text{(Cl)}^- \). Complex Q is \( \text{[Fe(H}_2\text{O)}_6\text{]}^{3+} \). Chloride ions are known to be ligands that can displace water molecules in coordination complexes.
The reaction would be a ligand substitution:
| \( \text{[Fe(H}_2\text{O)}_6\text{]}^{3+}\text{(aq)} \) | \( + \text{ Cl}^-\text{(aq)} \) | \( \longrightarrow \) | \( \text{[Fe(H}_2\text{O)}_5\text{(Cl)]}^{2+}\text{(aq)} \) | \( + \text{ H}_2\text{O(l)} \) |
| (Complex Q) | (from NaCl) | (Complex R) |
The proposed complex R in option 1 is \( \text{[Fe(H}_2\text{O)}_5\text{(Cl)]}^{2+} \). Chloro complexes of iron(III), like \( \text{[Fe(H}_2\text{O)}_5\text{(Cl)]}^{2+} \) or even \( \text{[FeCl}_4\text{]}^- \), are typically yellow. This matches the observed color change from pale violet (Q) back to yellow (R).
Summary of Species P, Q, and R
Based on the reactions and color changes described in the question, the species P, Q, and R consistent with the observations are:
- P: \( \text{[Fe(H}_2\text{O)}_5\text{(OH)]}^{2+} \) (yellow)
- Q: \( \text{[Fe(H}_2\text{O)}_6\text{]}^{3+} \) (pale violet)
- R: \( \text{[Fe(H}_2\text{O)}_5\text{(Cl)]}^{2+} \) (yellow)
These species and their transformations align perfectly with the reactions and colors given in the problem statement.
Important Questions from p - Block
Which of the following has the lowest boiling point?
Which of the following reaction(s) do(es) NOT occur
(i) [NPCl2]3 + 6 NaF \(\rm \xrightarrow[reflux]{MeCN}\) [NPF2]3 + 6 NaCl
(ii) n PCl5 + n NH4Cl \(\rm \xrightarrow[reflux]{C_6H_5Cl}\) [NPCl2]n + 4 n HCl [n = 3, 4, 5]
(iii) n PF 5 + n NH 4 F \(\rm \xrightarrow[reflux]{C_6H_5Cl}\) [NPF 2 ] n + 4 n HF [n = 3, 4, 5]
Choose the correct statement(s) from the following:
(i) The trend in Lewis acidity among silicon halides is SiI4 < SiBr4 < SiCl4 < SiF4.
(ii) Tin(II) chloride can act as a Lewis acid and not as a Lewis base.
(iii) Aluminosilicates can display Brønsted acidity.
Consider following statements
A. PbCl2 has low solubility in water.
B. Sulfides of As(III) and Sb(III) are soluble in ammonium sulfide.
C. SnS is soluble in yellow ammonium sulfide.
D. MnS is precipitated by passing H2S through acidic MnCl2.
Correct statements are
Which of the statements (A‐D) given below are correct for B2H6 molecule:
A. Addition of Et2O•BF3 to NaBH4 in a polyether solvent produces B2H6.
B. It has D2d symmetry.
C. Reaction of B2H6 with NMe3 gives Me3N•BH3.
D. It is diamagnetic.
