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151.

`BF_(3)` molecule has planar structure. Correct explanation for this isA. `BF_(3)` is `sp^(3)` hybridisedB. `BF_(3)` is `sp^(2)` hybridisedC. `BF_(3)` is sp hybridisedD. `BF_(3)` is `sp^(3)` hybridised

Answer» Correct Answer - B
In `BF_(3)`, B is `sp^(2)`-hybridised.
Discussion
152.

In commercial electrochemical process for Al extraction, electrolyte used isA. `Al(OH)_(3)` in `NaOH` solutionB. An aqueous solution of `Al_(2)(SO_(4))_(3)`C. A molten mixture of `Al_(2)O_(3)` and `Na_(3)AlF_(6)`D. A molten mixture of `Al(OH)_(3)` and `AlO(OH)`

Answer» Correct Answer - C
Al is extracted commercially by the electrolysis of a molten mixture of `Al_(2)O_(3)` (alumina) and `Na_(2)AlF_(6)` (cryolite).
Discussion
153.

Thermite is a mixture ofA. 3 parts of powdered Al and 1 part of `Fe_(2)O_(3)`B. 1 parts of powdered Al and 3 part of `Fe_(2)O_(3)`C. 1 parts of powdered Al and 1 part of `Fe_(2)O_(3)`D. 2 parts of powdered Al and 1 part of `Fe_(2)O_(3)`

Answer» Correct Answer - B
Thermite is a mixture of 3 parts (by weight) `Fe_(2)O_(3)` and 1 part (by weight) aluminium powder.
Discussion
154.

Alum is a water purifier because itA. softness hard waterB. coagulates the impuritiesC. destroys the pathogenic bacteriaD. gives taste

Answer» Correct Answer - B
Alum coagulates the suspended or colloidal impurities.
Discussion
155.

In the aluminothermic process, Al acts as a/anA. FluxB. Oxidising agentC. Reducing agentD. Solder

Answer» Correct Answer - C
In the aluminothermic process, aluminium acts as a reducing agent.
`Al+Fe_(2)O_(3) rarr Al_(2)O_(3)+Fe`
Discussion
156.

Which one of the following is not a use of potash alum ?A. As a styptic in arresting bleedingB. As a pesticideC. As a mordant in dyeingD. As a coagulant for colloidal clay in water

Answer» Correct Answer - B
Alum is not used as a pesticide.
Discussion
157.

The aqueous solution of potash alum isA. BasicB. AcidicC. NeutralD. None of these

Answer» Correct Answer - B
The aqueous solution of potash alum is acidic due to cationic hydrolysis of `Al^(3+)` ion provided by potash alum.
`Al^(3+)+3H_(2)Orarr Al (OH)_(3)+3H^(+)`.
Discussion
158.

Which of the following statements is not true about potash alum ?A. Its empirical formula is `Kal(SO_(4))_(2).12H_(2)O`B. Its aqueous sol. Is basic in natureC. It is used in dyeing industryD. On heating, it melts in its water of crystallisation.

Answer» Correct Answer - B
An aqueous solution of potash alum is acidic in nature.
Discussion
159.

Alum is used by dyers of clothesA. for fire proofing fabricsB. as first-aid for cutsC. for softening hard waterD. as mordant

Answer» Correct Answer - D
The `Al^(3+)` ions produced, when potash alum is dissolved in water, act as a mordant in the process of dyeing of clothes.
Discussion
160.

`H_(3)BO_(3)` when dissolved in heavy water givesA. `D_(3)O^(+)` ionB. `H_(3)O^(+)` ionsC. `HD_(2)O^(+)` ionsD. `DH_(2)O^(+)` ions.

Answer» Correct Answer - A
`H_(3)BO_(3)+D_(2)O rarr D^(+)+[B(OH)_(3)(OD)]^(-)`
Discussion