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Difficulty: Very hardDirect Factual Retrieval

Prior to the widespread adoption of the Haber-Bosch process for industrial ammonia synthesis, early twentieth-century chemical agriculture relied heavily on the Frank-Caro process to fix atmospheric nitrogen. Developed in the late 1890s by Adolph Frank and Nikodem Caro, this thermochemical pathway reacted calcium carbide with pure gaseous nitrogen at temperatures exceeding 1,000 degrees Celsius to yield calcium cyanamide. Although energy-intensive due to its reliance on electric arc furnaces to manufacture the initial calcium carbide substrate, the technique offered a viable alternative to depleting Chilean nitrate reserves.

Critically, historian of technology Elena Vance highlights that the agricultural efficacy of calcium cyanamide depended on its secondary hydrolysis in soil, a microbially mediated process that converted cyanamide into urea and subsequently into plant-absorbable ammonium. However, contemporary industrial chemists encountered a persistent operational hurdle: crude cyanamide contained residual dicyandiamide, a polymerization byproduct that inhibited nitrification enzymes in soil bacteria, thereby temporarily sterilizing agricultural plots if applied without prior aging. To suppress dicyandiamide formation during synthesis, Frank and Caro introduced calcium chloride catalysts into the carbide charge, which lowered the required reaction temperature and diminished side-chain polymerization. Despite this refinement, the synthetic pathway remained economically uncompetitive in regions lacking abundant hydroelectric power, ultimately limiting its market penetration prior to Haber-Bosch's catalytic breakthrough.

According to the passage, which of the following was explicitly introduced into the calcium carbide charge to limit the generation of dicyandiamide during synthesis?

  1. A
    Pure gaseous nitrogen supplied under extreme thermal conditions exceeding 1,000 degrees Celsius
  2. B
    Concentrated urea synthesized through microbially mediated hydrolysis
  3. A catalytic chloride compound designed to lower synthesis temperatures and curb side-chain polymerizationAnswer
  4. D
    Hydroelectric power reserves harnessed to regulate furnace energy output
  5. E
    Nitrification enzymes isolated from indigenous soil bacteria

Answer

A catalytic chloride compound designed to lower synthesis temperatures and curb side-chain polymerization
The correct response accurately paraphrases explicit passage detail. The text notes that Frank and Caro incorporated calcium chloride catalysts into the carbide charge specifically to reduce reaction temperatures and diminish the side-chain polymerization that formed dicyandiamide.

Step-by-Step Solution

1
Locate the specific target detail in the passage
Identify the sentence discussing the intervention used to suppress dicyandiamide formation during synthesis.
The question explicitly asks what was introduced into the calcium carbide charge to limit dicyandiamide generation.
2
Analyze the explicit text evidence
The passage states: 'To suppress dicyandiamide formation during synthesis, Frank and Caro introduced calcium chloride catalysts into the carbide charge, which lowered the required reaction temperature and diminished side-chain polymerization.'
Direct factual retrieval requires finding the exact textual match for the cause-and-effect relationship specified in the prompt.
3
Evaluate paraphrased answer choices against explicit evidence
Match 'calcium chloride catalysts' to 'A catalytic chloride compound designed to lower synthesis temperatures and curb side-chain polymerization.'
Correct GMAT Reading Comprehension factual answers paraphrase passage statements without altering core meaning or scope.

Key Concept

Direct Factual Retrieval from Complex Academic Text
Estimated Time:2m 0s
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Topics

Direct Factual Retrieval

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