To measure the quantity of MnCl₂ dissolved in an aqueous solution, it was completely converted to KMnO4 using the reaction,

MnCl₂ + K₂S₂O₈ + H₂O → KMnO₄ + H₂SO₄ + HCl (equation not balanced).

Few drops of concentrated HCl were added to this solution and gently warmed. Further, oxalic acid (225 mg) was added in portions till the colour of the permanganate ion disappeared. The quantity of MnCl₂ (in mg) present in the initial solution is ____.

(Atomic weights in g mol^–1: Mn = 55, Cl = 35.5)

In order to oxidise a mixture of one mole of each of FeC₂O₄, Fe2(C₂O₄)₃, FeSO₄ and Fe₂(SO₄)₃ in acidic medium, the number of moles of KMnO₄ required is

A 50 L gas stream was passed through a solution containing Cd²⁺ where H₂S (in gas stream) was retained as CdS. The mixture was acidified and treated with 50 mL of 0.004 M I₂. After the reaction S^2– + I₂ → S(s) + 2I^– was complete, the excess iodine was treated with 15 mL of 0.01 M thiosulphate. Calculate concentration of H₂S in ppm. Use density of gas stream = 1.7 g / L.

A gaseous mixture was passed at the rate of 2.5 L/min through a solution of NaOH for a total of 1 hour. The SO₂ in the mixture was retained as sulphite ion :

SO₂(g) + 2OH^– → SO₃^2– (g) + H₂O(ℓ)

After acidification with HCl the sulphite was titrated with 5 mL of 0.003 M KIO₃

IO₃^– + 2H₂SO₃ + 2Cl^– → 2SO₄^2– + ICl₂^– + 2H⁺ + H₂O

Calculate concentration of SO₂ in ppm if density of gaseous mixture is 1.6 g/L.

0.35 g of iron wire was dissolved in excess of dilute H₂SO₄ and solution was made upto 100 mL. 20 mL of this solution require 30 mL of $\frac{\mathrm{N}}{30}$ K₂Cr₂O₇ solution for exact oxidation. Calcualte % purity of Fe in wire.