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Iodometric titration: liberated iodine titrated with thiosulphate

This type of question, asked 4 times: 28 Jun 2022, 26 Jul 2022, 28 Jan 2026 S1, 6 Apr 2026 S2. All 4 questions below, oldest first.

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  1. Question 1

    28 Jun 2022

    51
    A 2.0 g2.0\text{ }g sample containing MnO2MnO_{2} is treated with HClHCl liberating Cl2Cl_{2}. The Cl2Cl_{2} gas is passed into a solution of KIKI and 60.0 mL60.0\text{ }mL of 0.1MNa2 S2O30.1MNa_{2}{\text{ }S}_{2}O_{3} is required to titrate the liberated iodine. The percentage of MnO2MnO_{2} in the sample is (Nearest integer) [Atomic masses (in u) Mn=55;Cl=35.5;O=16Mn = 55;Cl = 35.5;O = 16, I=127,Na=23, K=39, S=32]I = 127,Na = 23,\text{ }K = 39,\text{ }S = 32\rbrack

  2. Question 2

    26 Jul 2022

    145
    20 mL20\text{ }mL of 0.02M0.02M hypo solution is used for the titration of 10 mL10\text{ }mL of copper sulphate solution, in the presence of excess of KI using starch as an indicator. The molarity of Cu2+Cu^{2 +} is found to be ×10−2M\times10^{- 2}M [nearest integer] Given: 2Cu2++4I−→Cu2I2+I22Cu^{2 +}+ 4I^{-}\rightarrow Cu_{2}I_{2}+I_{2}
    I2+2 S2O3 2−→2I−+S4O6 2−I_{2}+ 2{\text{ }S}_{2}O_{3}\ ^{2 -}\rightarrow 2I^{-}+S_{4}O_{6}\ ^{2 -}

  3. Question 3

    28 Jan 2026 S1

    46
    500 mL of 1.2 M KI solution is mixed with 500 mL of 0.2MKMnO40.2M{KMnO}_{4} solution in basic medium. The liberated iodine was titrated with standard 0.1MNa2 S2O30.1M{Na}_{2}{\text{ }S}_{2}O_{3} solution in the presence of starch indicator till the blue color disappeared. The volume (in L ) of Na2 S2O3{Na}_{2}{\text{ }S}_{2}O_{3} consumed is ____\_\_\_\_ .(Nearest integer)

  4. Question 4

    6 Apr 2026 S2

    48
    500 mL of 0.2MMnO4−0.2M{MnO}_{4}^{-}solution in basic medium when mixed with 500 mL of 1.5 M KI solution, oxidises iodide ions to liberate molecular iodine. This liberated iodine is then titrated with a standard x M thiosulphate solution in presence of starch till the end point. If 300 mL of thiosulphate was consumed, then the value of x is ____\_\_\_\_ .