Which of the following statement is not true?
(correct answer +2, wrong answer -0.5)

N a_{2} C r_{2} O_{7}

is prefered over

K_{2} C r_{2} O_{7}

in volumetric analysis

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On passing

H_{2} S

through acidified

K_{2} C r_{2} O_{7}

solution a milky colour is observed

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K_{2} C r_{2} O_{7}

solution becomes yellow on increasing the

p H

beyond

7

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K_{2} C r O_{4}

solution becomes orange in color on decreasing the pH to acidic medium

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Solution

The correct option is A $N a_{2} C r_{2} O_{7}$ is prefered over $K_{2} C r_{2} O_{7}$ in volumetric analysis
A) $K_{2} C r_{2} O_{7}$ is used as a primary standard in volumetric
analysis.
B) On passing $H_{2} S$ through acidified $K_{2} C r_{2} O_{7}$ solution a milky colour is observed due to the formation of colloidal sulfur.
$K_{2} C r_{2} O_{7} + 4 H_{2} S O_{4} + 3 H_{2} S \to K_{2} S O_{4} + C r_{2} (S O_{4})_{3} + 7 H_{2} O + 3 S M i l k y (C o l l o i d a l s o l)$
C) $K_{2} C r_{2} O_{7}$ solution becomes yellow on increasing the $p H$ beyond $7$ due to the formation of $K_{2} C r O_{4}$
D) $K_{2} C r O_{4}$ solution becomes orange on decreasing the $p H$ below $7$ due to the formation of $K_{2} C r_{2} O_{7}$

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