1. Tardigrade
  2. Question
  3. Chemistry
  4. One gram of Na3AsO4 is boiled with excess of solid KI in presence of strong HCl. The iodine evolved is absorbed in KI solution and titrated against 0.2 N hyposolution. Assuming the reaction to be AsO3-4 + 2H+ + 2I- → AsO3-3 + H2O + I2, calculate the volume of thiosulphate hypo consumed. [Atomic weight of As = 75 ]

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Q. One gram of $Na_3AsO_4$ is boiled with excess of solid $KI$ in presence of strong $HCl$. The iodine evolved is absorbed in $KI$ solution and titrated against $0.2\, N$ hyposolution. Assuming the reaction to be
$AsO^{3-}_{4} + 2H^{+} + 2I^{-} \to AsO^{3-}_{3} + H_{2}O + I_{2}$, calculate the volume of thiosulphate hypo consumed. [Atomic weight of $As = 75$ ]

Redox Reactions

Solution:

image
molar mass $Na_{3}AsO_{4}$
$= 23 \times 3 + 75 + 16 \times 4$
molar mass $= 208$
$eq. of As O_{4}^{-}= \frac{1}{\left(\frac{208}{2}\right)}=\left(\frac{1}{104}\right)$
equivalent of $Na_{3}AsO_{4}=$ equivalent of$I_{2}$
$ =$ equivalent of $Na_{2} S_{2}O_{3}$
$\frac{1}{104}=.2 \times V$
$\frac{1}{104 \times.2}L=V =48.1 ML $