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Eight percent of the Earth's crust is aluminum, and there ar

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Eight percent of the Earth's crust is aluminum, and there ar [#permalink] New post 13 Jan 2020, 03:29
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Eight percent of the Earth's crust is aluminum, and there are hundreds of aluminum-bearing minerals and vast quantities of the rocks that contain them. The best aluminum ore. is bauxite, defined as aggregates of aluminous minerals, more or less impure, in which aluminum is present as hydrated oxides. Bauxite is the richest of all those aluminous rocks that occur in large quantities, and it yields alumina, the intermediate product required for the production of aluminum. Alumina also occurs naturally as the mineral corundum, but corundum is not found in large deposits of high purity, and therefore it is an impractical source for making aluminum. Most of the many abundant nonbauxite aluminous minerals are silicates, and, like all silicate minerals, they are refractory, resistant to analysis, and extremely difficult to process. The aluminum silicates are therefore generally unsuitable alternatives to bauxite because considerably more energy is required to extract alumina from them.
17. The author implies that a mineral must either be or readily supply which of the following in order to be classified as an aluminum ore?

(A) An aggregate
(B) Bauxite
(C) Alumina
(D) Corundum
(E) An aluminum silicate

[Reveal] Spoiler: OA
C


18. The passage supplies information for answering all of the following questions regarding aluminous minerals EXCEPT:

(A) What percentage of the aluminum in the Earth's crust is in the form of bauxite?
(B) Are aluminum-bearing nonbauxite minerals plentiful?
(C) Do the aluminous minerals found iIi bauxite contain hydrated oxides?
(D) Are aluminous hydrated oxides found in rocks?
(E) Do large quantities of bauxite exist?

[Reveal] Spoiler: OA
A


19. The author implies that corundum would be used to produce aluminum if

(A) corundum could be found that is not contaminated by silicates
(B) the production of alumina could be eliminated as an intermediate step in manufacturing aluminum
(C) many large deposits of very high-quality corundum were to be discovered
(D) new technologies were to make it possible to convert corundum to a silicate
(E) manufacturers were to realize that the world's supply of bauxite is not unlimited


[Reveal] Spoiler: OA
C


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Re: Eight percent of the Earth's crust is aluminum, and there ar [#permalink] New post 14 Jan 2020, 04:36
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1. The author implies that a mineral must either be or readily supply which of the following in order to be classified as an aluminum ore?

The passage says that "and it yields alumina, the intermediate product required for the production of aluminum". Therefore C is the best option.

2. The passage supplies information for answering all of the following questions regarding aluminous minerals EXCEPT:

Although it says "Bauxite is the richest of all those aluminous rocks that occur in large quantities", it does not specify a percentage, So option A is the answer.

3. The author implies that corundum would be used to produce aluminum if?

We can reference the answer from the sentence: Alumina also occurs naturally as the mineral corundum, but corundum is not found in large deposits. Hence option C fits best.
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Re: Eight percent of the Earth's crust is aluminum, and there ar [#permalink] New post 14 Jan 2020, 22:32
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Eight percent of the Earth's crust is aluminum, and there are hundreds of aluminum-bearing minerals and vast quantities of the rocks that contain them [Historical Facts]

The best aluminum ore. is bauxite [Main Idea], defined as aggregates of aluminous minerals, more or less impure, in which aluminum is present as hydrated oxides.

Bauxite is the richest of all those aluminous rocks [Supporting Main Idea] that occur in large quantities, and it yields alumina, the intermediate product required for the production of aluminum.

Alumina also occurs naturally as the mineral corundum, but corundum is not found in large deposits of high purity, and therefore it is an impractical source for making aluminum [Supporting Main Idea].

Most of the many abundant nonbauxite aluminous minerals are silicates, and, like all silicate minerals, they are refractory, resistant to analysis, and extremely difficult to process. [Supporting next sentence]

The aluminum silicates are therefore generally unsuitable alternatives to bauxite [Supporting Main Idea] because considerably more energy is required to extract alumina from them.
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Re: Eight percent of the Earth's crust is aluminum, and there ar [#permalink] New post 14 Jan 2020, 22:46
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Main idea:
The best aluminum ore. is bauxite [because it produces alumina]
Corundum [because corundum is not found in large deposits of high purity] and aluminum silicates [because they are extremely difficult to process] [b]are not suitable alternatives to bauxite. [/b]
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Re: Eight percent of the Earth's crust is aluminum, and there ar [#permalink] New post 14 Jan 2020, 22:51
BelalHossain wrote:
Main idea:
The best aluminum ore. is bauxite [because it produces alumina]
Corundum [because corundum is not found in large deposits of high purity] and aluminum silicates [because they are extremely difficult to process] [b]are not suitable alternatives to bauxite. [/b]


Q17:
WHY bauxite is The best aluminum ore?
because it produces alumina.
That means to be an aluminum ore, one has to produce/supply alumina.
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Re: Eight percent of the Earth's crust is aluminum, and there ar [#permalink] New post 14 Jan 2020, 22:54
BelalHossain wrote:
Main idea:
The best aluminum ore. is bauxite [because it produces alumina]
Corundum [because corundum is not found in large deposits of high purity] and aluminum silicates [because they are extremely difficult to process] [b]are not suitable alternatives to bauxite. [/b]


Ques 19: Why Corundum is not good alternative to bauxite? because corundum is not found in large deposits of high purity.
How Corundum can be a good alternative to bauxite>>>> if corundum is found in large deposits of high purity [Just crossing NOT from both side].
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Re: Eight percent of the Earth's crust is aluminum, and there ar [#permalink] New post 14 Jan 2020, 23:07
BelalHossain wrote:
Eight percent of the Earth's crust is aluminum, and there are hundreds of aluminum-bearing minerals and vast quantities of the rocks that contain them [Historical Facts]

The best aluminum ore. is bauxite [Main Idea], defined as aggregates of aluminous minerals, more or less impure, in which aluminum is present as hydrated oxides.

Bauxite is the richest of all those aluminous rocks [Supporting Main Idea] that occur in large quantities, and it yields alumina, the intermediate product required for the production of aluminum.

Alumina also occurs naturally as the mineral corundum, but corundum is not found in large deposits of high purity, and therefore it is an impractical source for making aluminum [Supporting Main Idea].

Most of the many abundant nonbauxite aluminous minerals are silicates, and, like all silicate minerals, they are refractory, resistant to analysis, and extremely difficult to process. [Supporting next sentence]

The aluminum silicates are therefore generally unsuitable alternatives to bauxite [Supporting Main Idea] because considerably more energy is required to extract alumina from them.


18. The passage supplies information for answering all of the following questions regarding aluminous minerals EXCEPT:

(A) What percentage of the aluminum in the Earth's crust is in the form of bauxite? First line does not give info about bauxite

(B) Are aluminum-bearing nonbauxite minerals plentiful?
Most of the many abundant nonbauxite aluminous minerals are silicates

(C) Do the aluminous minerals found iIi bauxite contain hydrated oxides?
The best aluminum ore. is bauxite [Main Idea], defined as aggregates of aluminous minerals, more or less impure, in which aluminum is present as hydrated oxides.

(D) Are aluminous hydrated oxides found in rocks?
Bauxite which is present as hydrated oxides is the richest of all those aluminous rocks

(E) Do large quantities of bauxite exist?
Bauxite is the richest of all those aluminous rocks [Supporting Main Idea] that occur in large quantities
Re: Eight percent of the Earth's crust is aluminum, and there ar   [#permalink] 14 Jan 2020, 23:07
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