Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing $pH$ on a solution of potassium dichromate?

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(N/A) Potassium dichromate is prepared from chromite ore $(FeCr_2O_4)$ in the following steps:
Step $(1):$ Preparation of sodium chromate
$4FeCr_2O_4 + 16NaOH + 7O_2 \longrightarrow 8Na_2CrO_4 + 2Fe_2O_3 + 8H_2O$
Step $(2):$ Conversion of sodium chromate into sodium dichromate
$2Na_2CrO_4 + 2H^+ \longrightarrow Na_2Cr_2O_7 + H_2O$
Step $(3):$ Conversion of sodium dichromate to potassium dichromate
$Na_2Cr_2O_7 + 2KCl \longrightarrow K_2Cr_2O_7 + 2NaCl$
Potassium dichromate is less soluble than sodium chloride and is obtained as orange-colored crystals.
The dichromate ion $(Cr_2O_7^{2-})$ exists in equilibrium with the chromate ion $(CrO_4^{2-})$ at $pH \approx 4$. Increasing the $pH$ (making the solution more basic) shifts the equilibrium towards the formation of chromate ions $(CrO_4^{2-})$ according to the reaction: $Cr_2O_7^{2-} + 2OH^- \longrightarrow 2CrO_4^{2-} + H_2O$.

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Correct statements from the following are:
$A$. Potassium dichromate is an oxidising agent and it oxidises $FeSO_4$ to $Fe_2(SO_4)_3$ in acidic medium.
$B$. Sodium dichromate can be used as primary standard in volumetric estimation.
$C$. $CrO_4^{2-}$ and $Cr_2O_7^{2-}$ are interconvertible in aqueous solution by varying the $pH$ of the solution.
$D$. $Cr-O-Cr$ bond angle in $Cr_2O_7^{2-}$ is $126^\circ$.
Choose the correct answer from the options given below:

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