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Redox titration calculations

55 questions on Redox titration calculations from the Redox Reactions chapter: 11 NEET level, 22 JEE Main, 22 JEE Advanced. Each one opens with its answer and solution.

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Equivalent mass of KMnO4 when it is reduced to Mn^2+ in acidic medium is (K = 39, Mn = 55, O = 16): NEET level
Equivalent mass of K2Cr2O7 as an oxidant in acidic medium (reduced to Cr^3+) is (K = 39, Cr = 52, O = 16): NEET level
When oxalic acid dihydrate, H2C2O4.2H2O (molar mass 126), is titrated against acidified KMnO4, its equivalent mass is: NEET level
In its reaction with iodine, 2S2O3^2- + I2 -> S4O6^2- + 2I-, the equivalent mass of Na2S2O3.5H2O (molar mass 248) is: NEET level
The normality of a 0.02 M solution of KMnO4 used in acidic medium (reduction to Mn^2+) is: NEET level
The normality of a 0.05 M solution of K2Cr2O7 used as an oxidant in acidic medium (reduction to Cr^3+) is: NEET level
In the iodometric titration of liberated iodine with sodium thiosulphate, starch indicator is added: NEET level
Dilute HCl is not used to acidify a KMnO4 titration because: NEET level
In acidic medium, 25 mL of 0.02 M KMnO4 can oxidise how many millimoles of Fe^2+ to Fe^3+? NEET level
In neutral medium KMnO4 is reduced to MnO2. Its equivalent mass in this medium is (K = 39, Mn = 55, O = 16): NEET level
1.5 mmol of I2 react completely with sodium thiosulphate (I2 + 2S2O3^2- -> 2I- + S4O6^2-). The amount of Na2S2O3 consumed is: NEET level
25 mL of 0.1 N oxalic acid is titrated with 0.02 M KMnO4 in acidic medium. The volume of permanganate needed is: JEE Main level
1.96 g of Mohr's salt, FeSO4.(NH4)2SO4.6H2O (molar mass 392), is dissolved in dilute H2SO4 and titrated with 0.02 M KMnO4. The volume of KMnO4 required is: JEE Main level
0.49 g of K2Cr2O7 (molar mass 294) is used in acidic medium to oxidise Fe^2+ to Fe^3+. The mass of iron(II) oxidised is (Fe = 56): JEE Main level
Copper(II) is determined iodometrically: 2Cu^2+ + 4I- -> 2CuI + I2, then I2 is titrated with thiosulphate. A sample liberates iodine that needs 20.0 mL of 0.100... JEE Main level
20.0 mL of a dilute hydrogen peroxide solution is titrated in acidic medium and requires 16.0 mL of 0.0500 M KMnO4. The concentration of H2O2 (molar mass 34) in... JEE Main level
A fixed volume of a KMnO4 solution is used to oxidise the same amount of a reductant, first in strongly acidic medium (to Mn^2+) and then in neutral medium (to ... JEE Main level
Dissolved oxygen is determined by the Winkler method: O2 oxidises Mn^2+, which then liberates iodine from iodide in acid; the iodine is titrated with thiosulpha... JEE Main level
10.0 mL of 0.0500 M K2Cr2O7 is treated with excess KI in acidic solution (Cr2O7^2- + 6I- + 14H+ -> 2Cr^3+ + 3I2 + 7H2O). The liberated iodine is titrated with 0... JEE Main level
0.72 g of ferrous oxalate, FeC2O4 (molar mass 144), is titrated in acidic medium with 0.02 M KMnO4. Both Fe^2+ and the oxalate are oxidised (Fe^3+ and CO2 forme... JEE Main level
Arsenic(III) oxide is determined by iodimetry: H3AsO3 + I2 + H2O -> H3AsO4 + 2I- + 2H+ (in a buffered medium). 0.099 g of As2O3 (molar mass 198) is dissolved to... JEE Main level
1.50 g of an impure sample of oxalic acid dihydrate, H2C2O4.2H2O (molar mass 126), is dissolved to make 250 mL of solution. A 25.0 mL portion requires 22.0 mL o... JEE Main level
To standardise a KMnO4 solution, 0.335 g of pure sodium oxalate, Na2C2O4 (molar mass 134), is dissolved in dilute H2SO4 and titrated hot, needing 41.7 mL of the... JEE Main level
The calcium in a 100 mL sample of hard water is precipitated as CaC2O4, filtered, dissolved in dilute H2SO4 and titrated with 0.0100 M KMnO4, which needs 12.4 m... JEE Main level
0.800 g of a copper ore is dissolved and treated with excess KI (2Cu^2+ + 4I- -> 2CuI + I2). The iodine liberated needs 24.0 mL of 0.100 M Na2S2O3. Find the per... JEE Main level
10.0 mL of a commercial H2O2 solution is diluted to 250 mL. A 25.0 mL portion of the diluted solution requires 18.0 mL of 0.0200 M KMnO4 in acidic medium. Find ... JEE Main level
0.800 g of an iron ore is dissolved and all the iron is converted to Fe^2+. It is titrated with 0.0200 M K2Cr2O7 in acidic medium, needing 28.0 mL. Find the per... JEE Main level
A vitamin C tablet is dissolved and titrated with 0.0500 M iodine solution, C6H8O6 + I2 -> C6H6O6 + 2HI; 28.4 mL of the iodine solution is needed. Find the mass... JEE Main level
3.675 g of K2Cr2O7 (molar mass 294) is dissolved in water to make 250 mL of solution. Find the normality of this solution when used as an oxidant in acidic medi... JEE Main level
Which of the following statements about permanganate titrations in the laboratory are correct? JEE Main level
In acidic medium, 1 mol of KMnO4 is equivalent to which of the following (all reactions quantitative)? JEE Main level
Which of the following statements about iodometry and iodimetry are correct? JEE Main level
20.0 mL of 0.0200 M KMnO4 in acidic medium is completely used up (no excess of either reagent) by which of the following? (H = 1, C = 12, O = 16, S = 32, Fe = 5... JEE Main level
0.435 g of an impure pyrolusite (MnO2, molar mass 87) is heated with 50.0 mL of 0.100 M oxalic acid in dilute H2SO4 (MnO2 + H2C2O4 + 2H+ -> Mn^2+ + 2CO2 + 2H2O)... JEE Advanced level
0.400 g of a sample containing KClO3 (molar mass 122.5) is reduced by 50.0 mL of 0.400 M Fe^2+ in acid (ClO3- + 6Fe^2+ + 6H+ -> Cl- + 6Fe^3+ + 3H2O). The excess... JEE Advanced level
A given volume of a KMnO4 solution oxidises 25.0 mL of 0.100 M FeSO4 completely in acidic medium. The same volume of this KMnO4 solution is used in neutral medi... JEE Advanced level
2.50 g of crude CuSO4.5H2O (molar mass 249.5) is dissolved to make 250 mL of solution. A 25.0 mL aliquot is treated with excess KI (2Cu^2+ + 4I- -> 2CuI + I2) a... JEE Advanced level
A mixture of oxalic acid (H2C2O4, molar mass 90) and potassium hydrogen oxalate (KHC2O4, molar mass 128) is analysed. One portion needs 15.0 mL of 0.100 M NaOH ... JEE Advanced level
5.00 g of bleaching powder is shaken with water and made up to 500 mL. A 25.0 mL portion is treated with excess KI and acid, and the iodine liberated needs 20.0... JEE Advanced level
0.120 g of pyrite, FeS2 (molar mass 120), is completely oxidised by acidified KMnO4 to Fe^3+ and SO4^2-. The volume of 0.0200 M KMnO4 needed is: JEE Advanced level
A sodium thiosulphate solution requires 20.0 mL of 0.0500 M I2 (I2 + 2S2O3^2- -> 2I- + S4O6^2-). An equal volume of the same thiosulphate solution is oxidised c... JEE Advanced level
A thiosulphate solution is standardised with KIO3 (molar mass 214). 0.2140 g of KIO3 reacts with excess KI in acid (IO3- + 5I- + 6H+ -> 3I2 + 3H2O) and the iodi... JEE Advanced level
2.00 g of a mixture of FeSO4 (molar mass 152) and Fe2(SO4)3 (molar mass 400) is dissolved in dilute H2SO4 and made up to 100 mL. A 20.0 mL portion needs 10.0 mL... JEE Advanced level
In neutral medium Mn^2+ is estimated by permanganate: 3Mn^2+ + 2MnO4- + 2H2O -> 5MnO2 + 4H+. A 25.0 mL sample of a manganese(II) solution needs 12.4 mL of 0.020... JEE Advanced level
50.0 mL of a water sample containing H2S is treated with 25.0 mL of 0.0500 M I2 solution (H2S + I2 -> S + 2H+ + 2I-). The excess iodine is back-titrated with 0.... JEE Advanced level
The chemical oxygen demand of waste water is estimated as follows. 20.0 mL of the sample is refluxed with 10.0 mL of 0.0250 M K2Cr2O7 in acid. The unreacted dic... JEE Advanced level
1.00 g of a chromium steel is treated so that all its chromium is converted to dichromate. After adding excess KI in acid, the liberated iodine needs 21.0 mL of... JEE Advanced level
2.00 g of a spirit sample is treated with 50.0 mL of 0.100 M K2Cr2O7 in excess acid; ethanol is oxidised to acetic acid (C2H5OH -> CH3COOH). Excess KI is then a... JEE Advanced level
Sodium thiosulphate (Na2S2O3.5H2O, molar mass 248) is oxidised to different products by different oxidants. Which statements are correct? JEE Advanced level
1.00 mmol of Na2SO3 (oxidised to sulphate) is titrated with 0.0200 M KMnO4 under different conditions. Which volumes of permanganate solution are required? JEE Advanced level
Which of the following statements about the iodometric titration of an oxidant (for example Cu^2+ or Cr2O7^2-) with thiosulphate are correct? JEE Advanced level
A solution is analysed for a reductant. 25.0 mL of it needs 20.0 mL of 0.0100 M K2Cr2O7 in acid, assuming a quantitative reaction. Which of the following could ... JEE Advanced level
1.390 g of a sample of impure ferrous sulphate heptahydrate, FeSO4.7H2O (molar mass 278, Fe = 56), is dissolved in dilute H2SO4 and titrated with 0.0400 M KMnO4... JEE Advanced level
0.100 g of a sample containing sodium nitrite (molar mass 69) is treated with 25.0 mL of 0.0200 M KMnO4 in acid (excess), NO2- going to NO3-. The unreacted perm... JEE Advanced level
In iodimetric determinations with I2 as the titrant (I = 127, As = 75, S = 32, C = 12, H = 1, O = 16), which equivalent masses are correct? JEE Advanced level