When chromite ore FeCr₂O₄ is fused with NaOH in presence of air, a yellow coloured compound
(A) is obtained which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCl forms a orange coloured crystalline compound (C).
(i) Write the formulae of the compounds (A), (B) and (C).
(ii) Write one use of compound (C).
(A) is obtained which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCl forms a orange coloured crystalline compound (C).
(i) Write the formulae of the compounds (A), (B) and (C).
(ii) Write one use of compound (C).
(i) 4FeCr₂O₄ + 16NaOH + 7O₂ → 8Na₂CrO₄ [A] + 2Fe₂O₃ + 8H₂O
2Na₂CrO₄ [A] + H₂SO₄ → Na₂Cr₂O₇ [B] + Na₂SO₄ + H₂O
Na₂Cr₂O₇ [B] + 2KCl → K₂Cr₂O₇ [C] + 2NaCl
A: Na₂CrO₄
B: Na₂Cr₂O₇
C: K₂Cr₂O₇
2Na₂CrO₄ [A] + H₂SO₄ → Na₂Cr₂O₇ [B] + Na₂SO₄ + H₂O
Na₂Cr₂O₇ [B] + 2KCl → K₂Cr₂O₇ [C] + 2NaCl
A: Na₂CrO₄
B: Na₂Cr₂O₇
C: K₂Cr₂O₇
Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with oxalic acid ?
Write the ionic equations for the reactions.
The electronic configuration of Cu(II) is 3d⁹ whereas that of Cu(I) is 3d¹⁰. Which of the following is correct?
(a) Cu(II) is more stable
(b) Cu(II) is less stable
(c) Cu(I) and Cu(II) are equally stable
(d) Stability of Cu(I) and Cu(II) depends on nature of copper salts
(i) Give reasons for the following :
(a) Compounds of transition elements are generally coloured.
(b) MnO is basic while Mn₂O₇ is acidic.
(ii) Calculate the magnetic moment of a divalent ion in aqueous medium if its atomic number is 26.
(i) Account for the following :
(a) Cu⁺ is unstable in an aqueous solution.
(b) Transition metals form complex compounds.
(ii) Complete the following equation :
CrO₂₇²⁻ + 8H⁺ + 3NO₂⁻ →
Suggest reasons for the following features of transition metal chemistry :
(i) The transition metals and their compounds are usually paramagnetic.
(ii) The transition metals exhibit variable oxidation states.
When KMnO₄ solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because
(a) CO₂ is formed as the product.
(b) The reaction is exothermic.
(c) MnO₄⁻ catalyses the reaction.
(d) Mn²⁺ acts as an auto-catalyst.
The following curve is obtained when molar conductivity is plotted against the square root of concentration, c½ for two electrolytes A and B :
Define the following terms :
(i) Fuel cell
(ii) Limiting molar conductivity
Calculate pH of following half-cell. Pt, \(H_2\) / \(H_2\)\(SO_4\) , if its electrode potential is 0.03V.
The conductivity of an aqueous solution of NaCl in a cell is 92 \(Ω^{−1}\) \(cm^{-1}\) the resistance offered by this cell is 247.8 Ω . Calculate the cell constant.
There are two possible reactions for cathode in the electrolysis of aqueous
\(ZnCl_2\) :\(Zn^{2+}\) (aq) + 2\(e^-\) → Zn(s) \(E^0\) = -0.76 V
2\(H_2\)O (l) + 2\(e^-\) → H2 (g) + 2\(OH^-\) (aq) \(E^0\) = - 0.83 V
Which one will take place? Why?
Define the following terms :
(i) Mole fraction
(ii) Isotonic solutions
(iii) Van’t Hoff factor
(iv) Ideal solution
(i) Following reactions occur at cathode during the electrolysis of aqueous silver chloride solution :
= +0.80 V
= 0.00 V
On the basis of their standard reduction electrode potential (E°) values, which reaction is feasible at the cathode and why ?
(ii) Define limiting molar conductivity. Why conductivity of an electrolyte solution decreases with the decrease in concentration ?