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The d-And-f-Block Elements

Multiple Choice Questions

311.
Assertion : Change in colour of acidic solution of potassium dichromate by breath is used to test drunk driver.
Reason : Change in colour is due to the complexation of alcohol with potassium di chromate.

If both assertion and reason are true and reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true, but reason is false.

Both assertion and reason are false statements.

If assertion is true, but reason is false.

Change in colour is clue to the oxidation or alcohol with potassium clichromate. Oxidation of alcohols with K₂Cr₂O₇ in dilute H₂SO₇ (orange solution):

K₂Cr₂O₇ in presence of dilute H₂SO₄ acts as an oxidising agent. It is converted into chromic sulphate which is green in colour.

$\underset{(orange)}{K_{2} {Cr}_{2} O_{7}} + 4 H_{2} {SO}_{4} \to K_{2} {SO}_{4} + \underset{(green)}{{Cr}_{2} ({SO}_{4})_{4}} + 4 H_{2} O + 3 O$

312.

Assertion : SiF₆^2- is known but SiCl₆^2- is not.

Reason : Size of fluorine is small and its lone pair of electrons interacts with d-orbitals of Si strongly.

If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.