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KVPY2017ChemistrySome Basic Concepts of Chemistry

A compound has the following composition by weight ; Na =18.60 %, ~S =25.80 %, H =4.02 % and O =51.58 % Assuming that all the hydrogen atoms in the compound are part of water of crystallization, the correct molecular formula of the compound is

Options

  1. ANa ₂ ~S ₂ O ₃ 3 H ₂ O
  2. BNa ₂ SO ₄ 5 H ₂ O
  3. CNa ₂ SO ₄ 10 H ₂ O
  4. DNa ₂ ~S ₂ O ₃ 5 H ₂ O

Correct answer

D. Na ₂ ~S ₂ O ₃ 5 H ₂ O

Step-by-step solution

array |c|c|c|c| Elements & % & moles & Simplest ratio Na & 18.6 & 18.6 23 =0.8 & 1 2 S & 25.8 & 25.8 32 =0.8 & 1 2 O & 51.58 & 51.58 16 =3.22 & 4 2 H & 4.02 & 4.02 1 =4.02 & 5 2 array Formula is Na ₂ ~S ₂ O ₃ 5 H ₂ O

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