Tag: aluminium

Questions Related to aluminium

Which of the following statement is incorrect?

aluminium patterns and properties of metals chemistry

  1. $Al$ reacts with excess $NaOH$ to give $Al{(OH)} _{3}$

  2. $NaH{CO} _{3}$ on heating gives ${Na} _{2}{CO} _{3}$

  3. Pure sodium metal dissolves in liquid ammonia to give blue solution

  4. $NaOH$ reacts with glass to give sodium silicate

Show answer
Correct Option: A
Explanation:

Sodium aluminate is also formed by the action of sodium hydroxide on elemental aluminium which is an amphoteric metal. The reaction is highly exothermic once established and is accompanied by the rapid evolution of hydrogen gas. The reaction is written as:
$2Al+2NaOH+{ 2H } _{ 2 }O\longrightarrow 2NaAlO _{ 2 }+3{ H }$

$2NaHCO _{ 3 (S) }\longrightarrow N{ a } _{ 2 }CO _{ 3 (S) }+CO _{ 2 (g) }+{ H } _{ 2 }O _{  (l) }$  This statment is correct.

By the reaction of sodium with liquid ammonia sodium ammide can be prepared.Sodium (alkali metal)dissolves in liquid ammoia solution to form a blue solution characteristic of a solvated electron in liquid ammonia, which is conducting in nature, due to ammoniated electrons (solvated electron).
This statment is correct.

Sodium silicate liquid can also be prepared directly by dissolving silica sand under pressure in a heated aqueous solution of caustic soda (sodium hydroxide, NaOH):
$2NaOH+{ SiO } _{ 2 }\longrightarrow Na _{ 2 }O.{ SiO } _{ 2 }+{ H } _{ 2 }O$
This statment is correct.

Alane is chemically:

aluminium patterns and properties of metals chemistry

  1. $AlH _3$

  2. $(AlH _3) _n$

  3. $LiAlH _4$

  4. none

Show answer
Correct Option: A
Explanation:

Alane is a hydride of aluminium.

It can be represented by the formula $AlH _3$.

Which of the following compounds can make clothes fire proof ?

aluminium patterns and properties of metals chemistry

  1. $FeSO _{4}$

  2. $Al _{2}(SO _{4}) _{3}$

  3. $Cu _{2}SO _{4}$

  4. $MgSO _{4}.7H _{2}O$

Show answer
Correct Option: B
Explanation:

$Al _2(SO _4) _3$ used to make fire proof clothes.

The hydroxide, which is soluble in excess of sodium hydroxide is:

aluminium patterns and properties of metals chemistry

  1. $Fe(OH) _{3}$

  2. $Cu(OH) _{2}$

  3. $Cr(OH) _{3}$

  4. $Al(OH) _{3}$

Show answer
Correct Option: D
Explanation:

Aluminium hydroxide is insoluble in $H _2O$ but it is soluble in strong acids and strong bases. This is because of $Al(OH) _3$ its amphoteric nature.

$Al(OH) _3 + NaOH \rightarrow Na[Al(OH) _4]$

Cryolite is:

aluminium patterns and properties of metals chemistry

  1. ${Na} _{3}Al{F} _{6}$ and is used in the electrolysis of alumina for decreasing electrical conductivity

  2. ${Na} _{3}Al{F} _{6}$ and is used in the electrolysis of alumina for lowering the melting point of alumina

  3. ${Na} _{3}Al{F} _{6}$ and is used in the electrolytic purification of alumina

  4. ${Na} _{3}Al{F} _{6}$ and is used in the electrolysis of alumina

Show answer
Correct Option: B,D
Explanation:
  • Molten cryolite $(Na _3AlF _6)$ is used as a solvent for aluminium oxide $(Al _2O _3)$ in the Hall–Héroult process, used in the refining of aluminium. 
  • It decreases the melting point of molten (liquid state) aluminium oxide to 900-1000 °C from 2000-2500 °C. Thus cryolite makes the extraction of aluminium profitable. 
  • Hence both option B and D are correct .

The incorrect statement among the following is:

aluminium patterns and properties of metals chemistry

  1. Bleaching powder is used as a germicide

  2. Chlorine is used in the preparation of

    insecticides like DDT.

  3. Fluorine is used in Rocket fuels

  4. $Na _{3}AlF _{3}$ is not a insecticide

Show answer
Correct Option: D
Explanation:

$Na _{3}AlF _{3}$ is used as a insecticide
So D is false

${ AlO } _{ 2 }^{ - }$ ion in aqueous solution exists as ?

aluminium patterns and properties of metals chemistry

  1. ${ \left[ Al{ \left( OH \right) } _{ 6 } \right] }^{ 2- }$

  2. ${ \left[ Al{ \left( OH \right) } _{ 4 }\left( { H } _{ 2 }O \right) \right] }^{ - }$

  3. ${ \left[ Al{ \left( OH \right) } _{ 4 }{ \left( { H } _{ 2 }O \right) } _{ 2 } \right] }^{ - }$

  4. ${ \left[ Al{ \left( OH \right) } _{ 6 } \right] }^{ - }$

Show answer
Correct Option: C

Which of the statement about aluminium is not correct?

aluminium patterns and properties of metals chemistry

  1. It liberates hydrogen from acid as well as alkalies

  2. It liberates hydrogen from acid but not from alkalies

  3. It liberates hydrogen from hot alkali solution

  4. It liberates hydrogen from boiling water

Show answer
Correct Option: B
Explanation:

Solution:- (B) It liberates hydrogen from acid but not from alkalies

Aluminium is an amphoteric metal and hence it reacts with both acids as well as bases.
Reaction of $Al$ with acid-
$2 Al + HCl \longrightarrow 2 Al{Cl} _{3} + 3 {H} _{2}$
Reaction of $Al$ with base-
$2 Al + 2 NaOH + 2 {H} _{2}O \longrightarrow 2 NaAl{O} _{2} + 3 {H} _{2}$

The common impurities present in bauxite are:

aluminium patterns and properties of metals chemistry

  1. ${ Fe } _{ 2 }{ O } _{ 3 },{ SiO } _{ 2 }$

  2. $NaCl,{ MgCl } _{ 2 }$

  3. ${ AlCl } _{ 3 },{ MgCl } _{ 2 }$

  4. ${ CaCl } _{ 2 },{ MgCl } _{ 2 }$

Show answer
Correct Option: A
Explanation:

Bauxite has a number of impurities in it including iron oxides(hematite and goethite), $Fe _2O _3$ the sand silicon dioxide $SiO _2$ the clay mineral Kaolinite and asmall amount of $TiO _2$ known as Anatase.

Hence option A is correct answer.

In the purification of $Al$ by Hoop's process the correct statement is 

aluminium patterns and properties of metals chemistry

  1. electrolytic cell is iron and it contains three layer mass

  2. upper layer is pure $Al$ and Carbon rods in it are cathode and the bottom layer contains impure $Al$ and carbon lining of the cell is anode

  3. Electrolyte is the middle layer with fused mixture of flouride.

  4. All of the above

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Correct Option: D