MCQ
$15\, mL$ of aqueous solution of $Fe ^{2+}$ in acidic medium completely reacted with $20\, mL$ of $0.03\, M$ aqueous $Cr _{2} O _{7}^{2-}$ The molarity of the $Fe ^{2+}$ solution is ........... $\times 10^{-2} M$ (Round off to the Nearest Integer).
  • A
    $32$
  • B
    $20$
  • $24$
  • D
    $42$

Answer

Correct option: C.
$24$
c
$n _{ eq } Fe ^{2+}= n _{ eq } Cr _{2} O _{7}^{2-}$

or, $\left(\frac{15 \times M _{ Fe ^{2+}}}{1000}\right) \times 1=\left(\frac{20 \times 0.03}{1000}\right) \times 6$

$\therefore M _{ Fe ^{2+}}=0.24 M =24 \times 10^{-2} M$

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