Soru

Zorluk: OrtaProcedural Steps

Passage

To extract and isolate fossilized pollen grains from lake sediment samples for palynological analysis, researchers follow a meticulous chemical purification process. First, the raw sediment sample is treated with hydrochloric acid (HClHCl) to dissolve carbonate minerals, such as limestone, which would otherwise obscure the microfossils. Once this reaction ceases, the mixture is centrifuged, and the supernatant liquid is decanted. Subsequently, to dissolve silicates—namely sand and clay particles—the remaining sediment residue is subjected to a bath of hydrofluoric acid (HFHF). This step requires extreme caution and thorough washing. Next, researchers perform acetolysis, exposing the washed residue to a mixture of acetic anhydride and sulfuric acid. This critical reaction digests organic debris, such as cellulose, leaving behind only the highly chemical-resistant outer walls of the pollen grains, known as the exine. Finally, the remaining material is rinsed, stained with dye, and mounted onto glass slides for microscopic identification.

Question

According to the passage, if a researcher omitted the step involving hydrofluoric acid (HFHF), what would be the most likely result?

  1. A
    The carbonate minerals, such as limestone, would remain in the sediment sample.
  2. Sand and clay particles would remain in the residue, obscuring the fossilized pollen grains.Cevap
  3. C
    The cellulose and other organic debris surrounding the pollen grains would not be digested.
  4. D
    The chemically resistant outer walls of the pollen grains would be degraded by subsequent rinses.

Cevap

Sand and clay particles would remain in the residue, obscuring the fossilized pollen grains.
According to the passage, hydrofluoric acid (HFHF) is introduced specifically to dissolve silicates, which the text explicitly defines as sand and clay particles. If this step is skipped, the sand and clay particles will not dissolve and will remain in the sediment residue, making it difficult to clearly observe the pollen grains under a microscope.

Adım Adım Çözüm

1
Identify the step in the passage that mentions the use of hydrofluoric acid (HFHF).
The passage states that hydrofluoric acid (HFHF) is used to dissolve silicates, which are sand and clay particles.
Understanding the function of this chemical is necessary to determine what occurs when it is omitted.
2
Analyze the consequence of omitting this specific step.
Without hydrofluoric acid (HFHF), the silicates (sand and clay particles) will not be dissolved and will remain in the final sample residue.
Omitting a procedural step means its intended chemical reaction will not take place, leaving the target impurities in the sample.
3
Evaluate the choices to locate the matching outcome.
The option stating that sand and clay particles would remain in the residue matches the outcome of omitting the hydrofluoric acid (HFHF) treatment.
This option accurately represents the consequence of skipping the silicate dissolution step.

Anahtar Kavram

Analyzing the chronological sequence and individual functions of steps in a scientific procedure to infer the consequences of procedural changes or omissions.
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