Question

How many moles of acidified $K_2Cr_2O_7$ is required to liberate $6$ moles of $I_2$ from an aqueous solution of $I^-$ ?

• A. 2
• B. 1
• C. 0.25
• D. 0.5

Answer 1

Answer: (A)

2

Answer 2

The balanced redox reaction will be:

$K _{2} Cr _{2} O _{7}+6 KI +7 H _{2} SO _{4} \rightarrow$
$4 K _{2} SO _{4}+3 I_{2}+ Cr _{2}\left( SO _{4}\right)_{3}+7 H _{2} O$
$3$ moles of $I_{2}$ requires $1$ mole of $K _{2} Cr _{2} O _{7}$

Hence, $6$ moles of $I_{2}$ will require $2$ moles of $K _{2} Cr _{2} O _{7}$