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The most common metal in the Earth’s crust, aluminum (or aluminium) wa

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The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 21 Nov 2017, 23:42
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The most common metal in the Earth’s crust, aluminum (or aluminium) was not discovered until 1825 because its isolated state is so reactive that free nuggets or flakes of the metal are never found in nature; rather, the metal is typically found as part of an amalgam, most commonly bauxite ore. Moreover, elemental aluminum is extremely difficult—and expensive—to separate from its ores by traditional chemical means. Indeed, the extreme reactivity of aluminum helps protect its modern, ubiquitous manifestations, such as aluminum foil. The surface of pure aluminum instantly combines with atmospheric oxygen to form a thin but robust “passivization” seal of aluminum oxide that prevents further corrosion. Many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.

For several decades after its discovery, aluminum was considered a precious metal and was more costly than gold or platinum, not because of any fundamental scarcity, but because of its elevated cost of production. The price of aluminum suddenly plummeted in 1886, however, when two 23-year-old inventors independently developed an electrolytic process of separating pure aluminum from a bath of molten aluminum salts, primarily cryolite. Cryolite itself is rare enough that synthetic salts eventually replaced it as the solution medium.

To answer this question, we must infer from facts given about iron. We are told that “many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.” Since we are also told that the oxide layer on aluminum is “thin but robust” and “prevents further corrosion,” we can logically infer that the oxide layer on iron does not prevent further corrosion as effectively as the layer on aluminum, and therefore iron in all likelihood corrodes more quickly than aluminum.

(A) CORRECT. This answer choice states our inference clearly.
(B) We can indeed conclude that iron oxides form more slowly (“not as swiftly”), but we cannot conclude that iron oxides form more robustly than aluminum oxides. In fact, we are told that aluminum oxide forms a “thin but robust… seal,” while iron oxides, among others, “do not form as… completely, or impermeably.” If the iron oxides are less complete and less impermeable, then we cannot infer that they are more robust; if anything, we should assume that they are less robust.
(C) We know that iron is less reactive than aluminum, but we cannot conclude that iron is therefore cheaper to isolate from its ores. The extreme reactivity of aluminum was the reason for the difficulty and expense of separating aluminum from its ores by traditional chemical means, but iron could also be expensive to extract from its ores by traditional chemical means; we simply don’t know enough about the extraction process to make an inference here.
(D) This choice is directly contradicted by the passage: it is aluminum that forms a more effective “passivization” seal, not iron.
(E) Although iron is less reactive than aluminum, we do not know whether it is more likely to be found in its isolated, elemental state. If anything, because it does not form as effective passivization seals, we would expect pure iron to corrode away in nature.

1. What can be most logically inferred from the passage about iron?

(A) It corrodes more quickly than aluminum.
(B) Its oxides form more slowly and robustly than those of aluminum.
(C) It is cheaper to isolate from its ores by traditional chemical means than aluminum.
(D) It is more susceptible to passivization than is aluminum.
(E) It is more commonly found in its isolated, elemental state.


This question asks us about a specific detail mentioned in the passage: the “passivization” layer on the surface of aluminum metal. The passage indicates that this layer: (1) is formed from the combination of atmospheric oxygen with the pure metal, (2) is thin but robust, and (3) prevents further corrosion. We should look for an answer that matches one of these facts.

(A) This choice reverses the stated cause-and-effect sequence. The layer is the result of the reaction between oxygen and aluminum—not the cause of that reaction.

(B) We are told that this layer is “thin but robust”; in fact, in the next sentence, we are told that the superficial (= surface) oxides of iron “do not form as swiftly, completely, or impermeably” (as the surface oxides of aluminum). Thus, the passivization layer on aluminum is actually more impenetrable than the one that forms on iron.

(C) We cannot conclude that this layer “lowers the utility” or usefulness of pure aluminum. If anything, we would guess that this layer, because it prevents further corrosion, makes pure aluminum very long-lasting and therefore more useful—and that guess would be an inference anyway.

(D) CORRECT. The passivization seal of aluminum oxide “prevents further corrosion” in aluminum, while “many other metals” do not form such seals “as swiftly, completely, or impermeably.” The passivization layer, then, provides aluminum with at least one advantage relative to other metals.

(E) We do not know whether this layer is what causes the “traditional” purification of aluminum to be an expensive process.

2. According to the passage, the natural passivization layer on the surface of aluminum metal

(A) causes atmospheric oxygen to react chemically with the metal
(B) is less impenetrable than typical iron oxide films formed on pure iron
(C) lowers the utility of aluminum in its uncontaminated state
(D) provides aluminum with a chemical advantage, relative to other metals
(E) precludes the inexpensive purification of the metal by traditional chemical processes


Spoiler: :: OE
To draw an economic comparison or analogy between what happened in 1886 (according to the passage) and a hypothetical situation, we first need to understand the significance of the stated events in that year. The passage tells us that, in 1886, two inventors developed a new process to isolate aluminum, and that as a result the price plummeted. We might predict that we are looking for a situation in which a previously expensive product suddenly becomes cheaper because of a new technology or process.

(A) While this situation captures a couple of the features of the events of 1886 (two researchers working independently make a discovery at the same time), these features do not imply anything about the economic impact of that discovery.

(B) This situation is in some ways opposite to the events of 1886. In this choice, a product containing one material (lead) is replaced by a product containing a “much rarer” material (lithium); if anything, we would expect the price of the product to go up, not down.

(C) In this choice, nothing is indicated or implied about the economic impact of replacing an old process (electronic signal processing) with a new process (direct processing of light signals). We do not know whether the new process would be cheaper or more expensive.

(D) This situation is in some ways opposite to the events of 1886. Here, a commodity becomes scarce, and the price shoots up.

(E) CORRECT. Expensive diamonds become less expensive due to the perfection of a new technological process: “low-cost artificial synthesis.” This situation would be directly analogous, in terms of economic impact, to what happened with aluminum in 1886.

3. In terms of economic impact, which of the following hypothetical situations would be most analogous to what the passage indicates happened in 1886?

(A) Fossil remains of a previously unknown dinosaur species are simultaneously discovered by two researchers working independently of one another.
(B) Lead-acid batteries are widely replaced in automobiles by batteries containing lithium, a much rarer metal than lead.
(C) Direct processing of light signals within fiber-optic devices supplants electronic signal processing performed by solid-state transistors.
(D) After supplies of a widely used commodity become unavailable, the price of the commodity surges.
(E) Low-cost artificial synthesis of diamonds, which are expensive to mine but composed of the common element carbon, is perfected.


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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 22 Nov 2017, 07:02
hazelnut wrote:
The most common metal in the Earth’s crust, aluminum (or aluminium) was not discovered until 1825 because its isolated state is so reactive that free nuggets or flakes of the metal are never found in nature; rather, the metal is typically found as part of an amalgam, most commonly bauxite ore. Moreover, elemental aluminum is extremely difficult—and expensive—to separate from its ores by traditional chemical means. Indeed, the extreme reactivity of aluminum helps protect its modern, ubiquitous manifestations, such as aluminum foil. The surface of pure aluminum instantly combines with atmospheric oxygen to form a thin but robust “passivization” seal of aluminum oxide that prevents further corrosion. Many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.

For several decades after its discovery, aluminum was considered a precious metal and was more costly than gold or platinum, not because of any fundamental scarcity, but because of its elevated cost of production. The price of aluminum suddenly plummeted in 1886, however, when two 23-year-old inventors independently developed an electrolytic process of separating pure aluminum from a bath of molten aluminum salts, primarily cryolite. Cryolite itself is rare enough that synthetic salts eventually replaced it as the solution medium.
To answer this question, we must infer from facts given about iron. We are told that “many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.” Since we are also told that the oxide layer on aluminum is “thin but robust” and “prevents further corrosion,” we can logically infer that the oxide layer on iron does not prevent further corrosion as effectively as the layer on aluminum, and therefore iron in all likelihood corrodes more quickly than aluminum.

(A) CORRECT. This answer choice states our inference clearly.
(B) We can indeed conclude that iron oxides form more slowly (“not as swiftly”), but we cannot conclude that iron oxides form more robustly than aluminum oxides. In fact, we are told that aluminum oxide forms a “thin but robust… seal,” while iron oxides, among others, “do not form as… completely, or impermeably.” If the iron oxides are less complete and less impermeable, then we cannot infer that they are more robust; if anything, we should assume that they are less robust.
(C) We know that iron is less reactive than aluminum, but we cannot conclude that iron is therefore cheaper to isolate from its ores. The extreme reactivity of aluminum was the reason for the difficulty and expense of separating aluminum from its ores by traditional chemical means, but iron could also be expensive to extract from its ores by traditional chemical means; we simply don’t know enough about the extraction process to make an inference here.
(D) This choice is directly contradicted by the passage: it is aluminum that forms a more effective “passivization” seal, not iron.
(E) Although iron is less reactive than aluminum, we do not know whether it is more likely to be found in its isolated, elemental state. If anything, because it does not form as effective passivization seals, we would expect pure iron to corrode away in nature.

1. What can be most logically inferred from the passage about iron?

(A) It corrodes more quickly than aluminum.
(B) Its oxides form more slowly and robustly than those of aluminum.
(C) It is cheaper to isolate from its ores by traditional chemical means than aluminum.
(D) It is more susceptible to passivization than is aluminum.
(E) It is more commonly found in its isolated, elemental state.


We are asked to determine the role that the second paragraph plays in the passage as a whole. In the first paragraph, the author introduces his main point – that seemingly unremarkable items can alter the course of history – and introduces nutmeg as an example. However, this example is incomplete at the end of the first paragraph. It is not until the second paragraph, when the example is further explored, that we learn how nutmeg actually altered the course of history.
(A) CORRECT. The second paragraph offers specific information – namely, the role that nutmeg played in the history of New York – to support the claim that seemingly unremarkable items can alter the course of history.
(B) The second paragraph does not summarize the evidence already given. It presents additional information.
(C) The second paragraph does not present the author's main point - that seemingly unremarkable items can alter the course of history. The main point is contained in the first paragraph.
(D) The second paragraph does demonstrate the relative importance of nutmeg in an event of historical significance, but it does not demonstrate the importance of historical change itself.
(E) The second paragraph does not discuss the outcomes, necessary or otherwise, of the author's claims. Instead, it offers evidence to support the claim made in the first sentence of the first paragraph.

2. For what purpose does the author include the second paragraph?

(A) It offers specific information to complete the logic of the author's claims.
(B) It summarizes and evaluates the evidence given thus far.
(C) It presents the author's main point to explain a unique situation.
(D) It cites a particular case to demonstrate the importance of historical change.
(E) It discusses the necessary outcome of the author's assertions.


This question asks us about a specific detail mentioned in the passage: the “passivization” layer on the surface of aluminum metal. The passage indicates that this layer: (1) is formed from the combination of atmospheric oxygen with the pure metal, (2) is thin but robust, and (3) prevents further corrosion. We should look for an answer that matches one of these facts.

(A) This choice reverses the stated cause-and-effect sequence. The layer is the result of the reaction between oxygen and aluminum—not the cause of that reaction.

(B) We are told that this layer is “thin but robust”; in fact, in the next sentence, we are told that the superficial (= surface) oxides of iron “do not form as swiftly, completely, or impermeably” (as the surface oxides of aluminum). Thus, the passivization layer on aluminum is actually more impenetrable than the one that forms on iron.

(C) We cannot conclude that this layer “lowers the utility” or usefulness of pure aluminum. If anything, we would guess that this layer, because it prevents further corrosion, makes pure aluminum very long-lasting and therefore more useful—and that guess would be an inference anyway.

(D) CORRECT. The passivization seal of aluminum oxide “prevents further corrosion” in aluminum, while “many other metals” do not form such seals “as swiftly, completely, or impermeably.” The passivization layer, then, provides aluminum with at least one advantage relative to other metals.

(E) We do not know whether this layer is what causes the “traditional” purification of aluminum to be an expensive process.

3. According to the passage, the natural passivization layer on the surface of aluminum metal

(A) causes atmospheric oxygen to react chemically with the metal
(B) is less impenetrable than typical iron oxide films formed on pure iron
(C) lowers the utility of aluminum in its uncontaminated state
(D) provides aluminum with a chemical advantage, relative to other metals
(E) precludes the inexpensive purification of the metal by traditional chemical processes



Not sure how Qs can have A as the answer-D looks clearly the right one to me.

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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 22 Nov 2017, 18:30
The Answer to Question 1..how is it option A?.....According to the passage, it's mentioned very clearly...Alum Oxides are the one that prevents Corrosion....whereas Iron is less reactive...which means it slowly reacts right?.....Please clarify further...all the OA's are very unreasonable
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 22 Nov 2017, 18:31
hazelnut wrote:
The most common metal in the Earth’s crust, aluminum (or aluminium) was not discovered until 1825 because its isolated state is so reactive that free nuggets or flakes of the metal are never found in nature; rather, the metal is typically found as part of an amalgam, most commonly bauxite ore. Moreover, elemental aluminum is extremely difficult—and expensive—to separate from its ores by traditional chemical means. Indeed, the extreme reactivity of aluminum helps protect its modern, ubiquitous manifestations, such as aluminum foil. The surface of pure aluminum instantly combines with atmospheric oxygen to form a thin but robust “passivization” seal of aluminum oxide that prevents further corrosion. Many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.

For several decades after its discovery, aluminum was considered a precious metal and was more costly than gold or platinum, not because of any fundamental scarcity, but because of its elevated cost of production. The price of aluminum suddenly plummeted in 1886, however, when two 23-year-old inventors independently developed an electrolytic process of separating pure aluminum from a bath of molten aluminum salts, primarily cryolite. Cryolite itself is rare enough that synthetic salts eventually replaced it as the solution medium.
To answer this question, we must infer from facts given about iron. We are told that “many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.” Since we are also told that the oxide layer on aluminum is “thin but robust” and “prevents further corrosion,” we can logically infer that the oxide layer on iron does not prevent further corrosion as effectively as the layer on aluminum, and therefore iron in all likelihood corrodes more quickly than aluminum.

(A) CORRECT. This answer choice states our inference clearly.
(B) We can indeed conclude that iron oxides form more slowly (“not as swiftly”), but we cannot conclude that iron oxides form more robustly than aluminum oxides. In fact, we are told that aluminum oxide forms a “thin but robust… seal,” while iron oxides, among others, “do not form as… completely, or impermeably.” If the iron oxides are less complete and less impermeable, then we cannot infer that they are more robust; if anything, we should assume that they are less robust.
(C) We know that iron is less reactive than aluminum, but we cannot conclude that iron is therefore cheaper to isolate from its ores. The extreme reactivity of aluminum was the reason for the difficulty and expense of separating aluminum from its ores by traditional chemical means, but iron could also be expensive to extract from its ores by traditional chemical means; we simply don’t know enough about the extraction process to make an inference here.
(D) This choice is directly contradicted by the passage: it is aluminum that forms a more effective “passivization” seal, not iron.
(E) Although iron is less reactive than aluminum, we do not know whether it is more likely to be found in its isolated, elemental state. If anything, because it does not form as effective passivization seals, we would expect pure iron to corrode away in nature.

1. What can be most logically inferred from the passage about iron?

(A) It corrodes more quickly than aluminum.
(B) Its oxides form more slowly and robustly than those of aluminum.
(C) It is cheaper to isolate from its ores by traditional chemical means than aluminum.
(D) It is more susceptible to passivization than is aluminum.
(E) It is more commonly found in its isolated, elemental state.


We are asked to determine the role that the second paragraph plays in the passage as a whole. In the first paragraph, the author introduces his main point – that seemingly unremarkable items can alter the course of history – and introduces nutmeg as an example. However, this example is incomplete at the end of the first paragraph. It is not until the second paragraph, when the example is further explored, that we learn how nutmeg actually altered the course of history.
(A) CORRECT. The second paragraph offers specific information – namely, the role that nutmeg played in the history of New York – to support the claim that seemingly unremarkable items can alter the course of history.
(B) The second paragraph does not summarize the evidence already given. It presents additional information.
(C) The second paragraph does not present the author's main point - that seemingly unremarkable items can alter the course of history. The main point is contained in the first paragraph.
(D) The second paragraph does demonstrate the relative importance of nutmeg in an event of historical significance, but it does not demonstrate the importance of historical change itself.
(E) The second paragraph does not discuss the outcomes, necessary or otherwise, of the author's claims. Instead, it offers evidence to support the claim made in the first sentence of the first paragraph.

2. For what purpose does the author include the second paragraph?

(A) It offers specific information to complete the logic of the author's claims.
(B) It summarizes and evaluates the evidence given thus far.
(C) It presents the author's main point to explain a unique situation.
(D) It cites a particular case to demonstrate the importance of historical change.
(E) It discusses the necessary outcome of the author's assertions.


This question asks us about a specific detail mentioned in the passage: the “passivization” layer on the surface of aluminum metal. The passage indicates that this layer: (1) is formed from the combination of atmospheric oxygen with the pure metal, (2) is thin but robust, and (3) prevents further corrosion. We should look for an answer that matches one of these facts.

(A) This choice reverses the stated cause-and-effect sequence. The layer is the result of the reaction between oxygen and aluminum—not the cause of that reaction.

(B) We are told that this layer is “thin but robust”; in fact, in the next sentence, we are told that the superficial (= surface) oxides of iron “do not form as swiftly, completely, or impermeably” (as the surface oxides of aluminum). Thus, the passivization layer on aluminum is actually more impenetrable than the one that forms on iron.

(C) We cannot conclude that this layer “lowers the utility” or usefulness of pure aluminum. If anything, we would guess that this layer, because it prevents further corrosion, makes pure aluminum very long-lasting and therefore more useful—and that guess would be an inference anyway.

(D) CORRECT. The passivization seal of aluminum oxide “prevents further corrosion” in aluminum, while “many other metals” do not form such seals “as swiftly, completely, or impermeably.” The passivization layer, then, provides aluminum with at least one advantage relative to other metals.

(E) We do not know whether this layer is what causes the “traditional” purification of aluminum to be an expensive process.

3. According to the passage, the natural passivization layer on the surface of aluminum metal

(A) causes atmospheric oxygen to react chemically with the metal
(B) is less impenetrable than typical iron oxide films formed on pure iron
(C) lowers the utility of aluminum in its uncontaminated state
(D) provides aluminum with a chemical advantage, relative to other metals
(E) precludes the inexpensive purification of the metal by traditional chemical processes




All the answers seem very deviating from the Passage....particularly the one with A's....any explanation given ?
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 27 Nov 2017, 19:46
2.5 minutes in total including reading the passage and all correct :-)
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 27 Nov 2017, 19:51
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Tridhipal wrote:
The Answer to Question 1..how is it option A?.....According to the passage, it's mentioned very clearly...Alum Oxides are the one that prevents Corrosion....whereas Iron is less reactive...which means it slowly reacts right?.....Please clarify further...all the OA's are very unreasonable


"Many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably" - in this line, it nowhere says explicitly that "iron oxides more slowly....." It's a trap option. But since it's written that iron is less reactive than aluminum, we reach the conclusion that it's not able to form the "passivization seal' as aluminium that prevents corrosion. Thus option (A). Hope it's clear!
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 27 Nov 2017, 20:23
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Tridhipal wrote:
The Answer to Question 1..how is it option A?.....According to the passage, it's mentioned very clearly...Alum Oxides are the one that prevents Corrosion....whereas Iron is less reactive...which means it slowly reacts right?.....Please clarify further...all the OA's are very unreasonable



Passage excerpt: The surface of pure aluminum instantly combines with atmospheric oxygen to form a thin but robust “passivization” seal of aluminum oxide that prevents further corrosion. Many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.

Aluminium + oxygen = aluminium oxide - prevents aluminium from corrosion
Iron is less reactive => can not form iron oxide to prevent iron from corrosion, as was the case of aluminium--> because their oxides do not form swiftly.

==> Iron corrodes more quickly than aluminum.
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post Updated on: 03 Mar 2018, 09:17
For question 1) A is right because

- Passage states “ores” specifically result in no corrosion
- The ore of aluminium is built very quickly….much faster than iron ore


Hence given iron has a slower pace for creation of iron ore….fact that iron ore is created slower hence iron corrodes faster

Originally posted by jabhatta@umail.iu.edu on 03 Mar 2018, 09:13.
Last edited by jabhatta@umail.iu.edu on 03 Mar 2018, 09:17, edited 1 time in total.
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 03 Mar 2018, 09:15
For Question 1) E is wrong because

Passage states that aluminum is never found in its elemental state hence (I assumed) Iron must be found more common in its elemental statement …

BUT there is another possibility too ….iron too is never found in its elemental state either

Hence E is not necessarily true ...hence wrong
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 16 May 2018, 21:31
Tridhipal wrote:
The Answer to Question 1..how is it option A?.....According to the passage, it's mentioned very clearly...Alum Oxides are the one that prevents Corrosion....whereas Iron is less reactive...which means it slowly reacts right?.....Please clarify further...all the OA's are very unreasonable



The Answer is A. Corrodes means to be destroyed or damaged, but corrosion is a chemical phenomenon. in the passage it is stated that Aluminium undergoes corrosion that means it wont get corroded afterwards, but the case of iron the case is inverse of the Aluminium.
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 19 May 2018, 11:43
can someone please help me with Question 2 and 4?.
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The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 20 May 2018, 10:17
kanthaliya wrote:
Tridhipal wrote:
The Answer to Question 1..how is it option A?.....According to the passage, it's mentioned very clearly...Alum Oxides are the one that prevents Corrosion....whereas Iron is less reactive...which means it slowly reacts right?.....Please clarify further...all the OA's are very unreasonable



The Answer is A. Corrodes means to be destroyed or damaged, but corrosion is a chemical phenomenon. in the passage it is stated that Aluminium undergoes corrosion that means it wont get corroded afterwards, but the case of iron the case is inverse of the Aluminium.


Yes, corrodes means getting damaged or destroyed.

It stated that " The surface of pure aluminium instantly combines with atmospheric oxygen to form a thin but robust “passivization” seal of aluminium oxide that prevents further corrosion. Many other metals, such as iron, are less reactive than aluminium, but their superficial oxides do not form as swiftly, completely, or impermeably.

Blue==> Aluminum Oxide prevents further corrosion..it implies it is undergoing damage and Aluminum Oxide prevents further damage.
Other metals (ex iron etc) < less reactive than Aluminum. ==> Aluminum is more reactive and hence prevents corrosion, SO Other metals as Iron are less reactive ==> causes to corrosion or corrodes more quickly (bcoz its less reactive compared to AL, which prevents corrosion)
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 20 May 2018, 10:50
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er.arun88 wrote:
can someone please help me with Question 2 and 4?.


There are only 3 Questions... So I assume u need help with Q2

According to the passage, the natural passivization layer on the surface of aluminum metal ---> Its asking what can be inferred abt Natural Passivization layer on the Surface of Al metal. So lets read the content of it..... i.e.

The surface of pure aluminum instantly combines with atmospheric oxygen to form a thin but robust “passivization” seal of aluminum oxide that prevents further corrosion. ==> Metal Aluminium prevents further corrosion which implies...there is no further damage .

Many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.==> Aluminium is more reactive than other metals.

Till this end, we can infer that either Aluminium has special characteristic or benefit. SO let's check the choices.

(A) causes atmospheric oxygen to react chemically with the metal --- Aluminium combines with atmospheric oxygen to form oxide, but AL is not the cause.
(B) is less impenetrable than typical iron oxide films formed on pure iron --- It is mentioned that "...but their superficial oxides do not form as swiftly, completely, or impermeably" ==> their refers to other metals and their oxides are not as impermeable as Al, so this implies AL is more impenetrable---This choice is opposite of what is stated in the passage..
(C) lowers the utility of aluminum in its uncontaminated state --- No info given about its uncontaminated state.
(D) provides aluminum with a chemical advantage, relative to other metals --- this is something similar we inferred
(E) precludes the inexpensive purification of the metal by traditional chemical processes --- Cryolite does it not the Surface layer of AL

So the option which can be inferred is . D

Hope this helps !
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 12 Jun 2018, 01:29
A Doesnt make a lot sense. The passage states:
The surface of pure aluminum instantly combines with atmospheric oxygen to form a thin but robust “passivization” seal of aluminum oxide that prevents further corrosion. Many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.

The lines suggest that aluminium corrodes more quickly "initially" to form a stable oxide preventing further corrosion. I do not think anything in the passage suggests that iron corrodes more quickly than aluminium. At best it suggests that the iron corrodes more quickly than the aluminum oxide. Which is not the question asked. I'd have to say I cant agree a bit with the answer.
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Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa  [#permalink]

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New post 17 Jul 2018, 06:34
Tridhipal wrote:
er.arun88 wrote:
can someone please help me with Question 2 and 4?.


There are only 3 Questions... So I assume u need help with Q2

According to the passage, the natural passivization layer on the surface of aluminum metal ---> Its asking what can be inferred abt Natural Passivization layer on the Surface of Al metal. So lets read the content of it..... i.e.

The surface of pure aluminum instantly combines with atmospheric oxygen to form a thin but robust “passivization” seal of aluminum oxide that prevents further corrosion. ==> Metal Aluminium prevents further corrosion which implies...there is no further damage .

Many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.==> Aluminium is more reactive than other metals.

Till this end, we can infer that either Aluminium has special characteristic or benefit. SO let's check the choices.

(A) causes atmospheric oxygen to react chemically with the metal --- Aluminium combines with atmospheric oxygen to form oxide, but AL is not the cause.
(B) is less impenetrable than typical iron oxide films formed on pure iron --- It is mentioned that "...but their superficial oxides do not form as swiftly, completely, or impermeably" ==> their refers to other metals and their oxides are not as impermeable as Al, so this implies AL is more impenetrable---This choice is opposite of what is stated in the passage..
(C) lowers the utility of aluminum in its uncontaminated state --- No info given about its uncontaminated state.
(D) provides aluminum with a chemical advantage, relative to other metals --- this is something similar we inferred
(E) precludes the inexpensive purification of the metal by traditional chemical processes --- Cryolite does it not the Surface layer of AL

So the option which can be inferred is . D

Hope this helps !

elemental aluminum is extremely difficult—and expensive—to separate from its ores by traditional chemical means. Can Option E be inferred from this statement
Re: The most common metal in the Earth’s crust, aluminum (or aluminium) wa &nbs [#permalink] 17 Jul 2018, 06:34
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