Chemistry · Mole concept, molar mass, percentage composition, empirical and molecular formulae

of a hydrated salt contains of iron, of sulphur of oxygen and 0.4532 g of water

\( 1.00 \mathrm{g} \) of a hydrated salt contains \( 0.2014 \mathrm{g} \) of iron, \( 0.1153 \mathrm{g} \) of sulphur \( 0.2301 \mathrm{g} \) of oxygen and 0.4532 g of water of crystallisation. If its empirical formula \( (\boldsymbol{F e}=\mathbf{5 6} ; \boldsymbol{S}=\mathbf{3 2} ; \mathbf{0}=\mathbf{1 6}) \) is \( F e S O_{x} \cdot y H_{z} O, \) then find the value of \( x, y \) and \( z \)

  • A. \( x=4, y=7, z=2 \)
  • B. \( x=3, y=6, z=2 \)
  • C. \( x=4, y=6, z=3 \)
  • D. None of these

Step-by-step solution

From the given masses, moles of Fe = 0.2014/56 = 0.003596, S = 0.1153/32 = 0.003603, O = 0.2301/16 = 0.01438. Dividing by smallest gives Fe:S:O ≈ 1:1:4, so x=4. Moles of water = 0.4532/18 = 0.02518. Ratio water:Fe = 0.02518/0.003596 ≈ 7, so y=7. Water is H2O, so z=2.
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