The most common metal in the Earths crust, aluminum (or aluminium)

Question

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.   1 
 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.

2 
 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

3 
 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.

Manhattan CAT 5

ishpreetanand · Answer

"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!

TaN1213 · Answer

Official Explanations:

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.

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.

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

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. 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.

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.

Sajjad1994 · Answer

Official Explanation

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

Exlanation

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.

Answer: E

arushi118 · Answer

In this explanation, you see price as the factor to which the statement is analogous. But if we assume "rarity of the material being substituted, then we would get option B. How to choose between the two?

guddo · Answer

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

The passage says aluminum used to be very expensive not because it was truly rare, but because it was very hard and costly to extract from ore. Then, in 1886, a new production process made extraction much cheaper, so the price fell sharply.  The key idea  is that  a valuable material made from a common underlying substance suddenly becomes much cheaper because a low-cost production method is developed .

(A) Fossil remains of a previously unknown dinosaur species are simultaneously discovered by two researchers working independently of one another.

This matches only the detail that two people made the discovery independently. It does not match the economic effect, which is a major drop in production cost and price.

(B) Lead-acid batteries are widely replaced in automobiles by batteries containing lithium, a much rarer metal than lead.

This goes the wrong way. It describes switching to a rarer material, not finding a cheap way to produce a formerly expensive material from something common.

(C) Direct processing of light signals within fiber-optic devices supplants electronic signal processing performed by solid-state transistors.

This is a technological change, but it does not clearly match the economic pattern in the passage. The passage is specifically about drastic cost reduction in producing a material.

(D) After supplies of a widely used commodity become unavailable, the price of the commodity surges.

This is the opposite economic effect. In the passage, price drops because production becomes cheaper.

(E) Low-cost artificial synthesis of diamonds, which are expensive to mine but composed of the common element carbon, is perfected.

This matches best. Diamonds are expensive not because carbon is rare, but because obtaining diamonds is costly. If a cheap artificial method is perfected, the price would fall in the same way aluminum’s price fell after a cheap extraction process was developed.

Answer: (E)

adebitis · Answer

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.

The correct answer is  (C) .
To find the answer, you have to look at the "price history" logic presented in the passage.
 
Analysis of the Options
 
  (A) It corrodes more quickly than aluminum. 
 
  Why it is wrong:  The passage says the surface of pure aluminum "instantly" combines with oxygen. Aluminum actually reacts  faster  than iron. The difference is that aluminum’s reaction creates a protective seal, while iron’s reaction (rust) keeps eating away at the metal. Aluminum reacts fast to save itself; iron reacts slower but eventually destroys itself.  
 
  (B) Its oxides form more slowly and robustly than those of aluminum. 
 
  Why it is wrong:  The text specifically says that iron's oxides do  not  form as "robustly" or "impermeably" as aluminum's. Iron rust is weak and flaky, not robust.  
 
  (C) It is cheaper to isolate from its ores by traditional chemical means than aluminum. 
 
  Why it is the correct answer:  The passage states that aluminum was more expensive than gold for decades because it was  "extremely difficult—and expensive—to separate from its ores by traditional chemical means."  Since iron has been used by humans for thousands of years using traditional furnaces (smelting), and wasn't considered a "precious metal" like aluminum was in the 1800s, we can logically infer that iron is much cheaper and easier to isolate using those old methods.  
 
  (D) It is more susceptible to passivization than is aluminum. 
 
  Why it is wrong:  Aluminum is the "king" of passivization in this text. Iron's failure to passivate (to form a tight, protective seal) is exactly why it rusts away while aluminum foil stays shiny.  
 
  (E) It is more commonly found in its isolated, elemental state. 
 
  Why it is wrong:  The passage doesn't give us enough information to know how iron is found in nature. It only tells us that aluminum is  never  found in its isolated state. We can't assume iron is different based on this text alone.

The most common metal in the Earths crust, aluminum (or aluminium)

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The most common metal in the Earths crust, aluminum (or aluminium)

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