Given below are two statements Statement I : Aqueous solution of $\mathrm{K}_{2}\mathrm{Cr}_{2}\mathrm{O}_{7}$ is preferred as a primary standard in volumetric analysis over $\mathrm{Na}_{2}\mathrm{Cr}_{2}\mathrm{O}_{7}$ aqueous solution Statement II : $\mathrm{K}_{2}\mathrm{Cr}_{2}\mathrm{O}_{7}$ has a higher solubility in water than $\mathrm{Na}_{2}\mathrm{Cr}_{2}\mathrm{O}_{7}$ In the light of the above statements, choose the correct answer from the options given below:

(C) Both Statement I is true but Statement II is false

(A) Both Statement I and Statement II are true

(B) Both Statement I and Statement II are false

(D) Both Statement I is false but Statement II is true

d and f Block Elements — JEE Main · 2023 · 10 Apr 2023 · Shift 1 Question with Solution

Given below are two statements

Statement I : Aqueous solution of

K_{2} Cr_{2} O_{7}

is preferred as a primary standard in volumetric analysis over

Na_{2} Cr_{2} O_{7}

aqueous solution
Statement II :

K_{2} Cr_{2} O_{7}

has a higher solubility in water than

Na_{2} Cr_{2} O_{7}

In the light of the above statements, choose the correct answer from the options given below:

(A)Both Statement I and Statement II are true
(B)Both Statement I and Statement II are false
(C)Both Statement I is true but Statement II is false✓ Correct
(D)Both Statement I is false but Statement II is true

Answer: (C)

Solution

A primary standard must be available in a pure, stable and non-hygroscopic form so that a solution of accurately known strength can be made by direct weighing. Potassium dichromate satisfies this: it is not hygroscopic, can be obtained very pure and its solution keeps its concentration, so it is the preferred primary standard. Sodium dichromate is deliquescent and cannot be weighed reliably, so it is not used as a primary standard, which makes the first statement true. As for solubility, sodium salts are generally more soluble in water than the corresponding potassium salts, so sodium dichromate is in fact more soluble than potassium dichromate; the claim that the potassium salt is more soluble is wrong, so the second statement is false. Statement I is true while Statement II is false.

JEE Main · 2023 · 10 Apr 2023 · Shift 1 · Single correct option

JEE Main · 2023 · 10 Apr 2023 · Shift 1 · d and f Block Elements

Solution

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