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  • Which one of the following benefaction process is used for the mineral <img alt="\mathrm{Al_{2}O_{3}.2H_{2}O}" src="https://entrancecorner.oncodecogs.com/gif.latex?%5Cmathrm%7BAl_%7B2%7DO

Which one of the following benefaction process is used for the mineral \mathrm{Al_{2}O_{3}.2H_{2}O}?

Option: 1

Froth floatation


Option: 2

Leaching


Option: 3

Liquation


Option: 4

Magnetic separation


Answers (1)

best_answer

Leaching is done for concentrating of ore.

In this method, the powdered ore is treated with a suitable chemical reagent which dissolves the ore while impurities remain insoluble in that reagent.


\mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{s})+2 \mathrm{NaOH}(\mathrm{aq})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{Na}\left[\mathrm{Al(OH)}_{4}\right](\mathrm{aq})
The sodium aluminate present in the solution is neutralized by passing CO2 gas and hydrated Al2O3 is precipitated. At this stage, a small amount of freshly prepared sample of hydrated Al2O3 is added to the solution. This is called seeding. It induces precipitation.

2 \mathrm{Na}\left[\mathrm{Al}(\mathrm{OH})_{4}\right](\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{g}) \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}.\mathrm{xH}_{2} \mathrm{O}(\mathrm{s})+2 \mathrm{NaHCO}_{3}(\mathrm{aq})

Sodium silicate remains in the solution and hydrated alumina is filtered, dried, and heated to give back pure Al2O3.

\mathrm{Al}_{2} \mathrm{O}_{3}.\mathrm{xH}_{2} \mathrm{O}(\mathrm{s}) \stackrel{1470 \mathrm{K}}{\longrightarrow} \mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{s})+\mathrm{xH}_{2} \mathrm{O}(\mathrm{g})

Therefore, option number (2) is correct.

Posted by

Ritika Jonwal

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