Pick the incorrect statement about common petroleum tests and crude characterisation indices. Identify the one that is factually wrong.
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APensky–Martens apparatus is used for determining flash points above 50 °C.
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BThe characterisation factor of paraffinic crude oil is more than 12.
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CAbel apparatus is used for determining flash points below 50 °C.
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DAn oil that shows a large change of viscosity with temperature has a high viscosity index.
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ECleveland open cup is typically used for high flash point materials.
Answer
Correct Answer: An oil that shows a large change of viscosity with temperature has a high viscosity index.
Explanation
Introduction:This question checks familiarity with standard petroleum test methods and indices: flash point apparatus selection (Abel, Pensky–Martens, Cleveland) and the meaning of the viscosity index (VI), as well as the UOP K/characterisation factor trend for crude types. Knowing which statements are correct versus incorrect is crucial for QA/QC and specification work.
Given Data / Assumptions:
- Abel is commonly applied to low flash point materials (generally below about 50 °C).
- Pensky–Martens (closed cup) is used for mid-range flash points (above roughly 50 °C).
- Paraffinic crude typically has a characterisation factor greater than 12.
- High viscosity index (VI) means viscosity changes little with temperature.
Concept / Approach:Evaluate each statement against standard definitions: the viscosity index is inversely related to viscosity’s temperature sensitivity. A high VI indicates relatively stable viscosity across temperature changes. Therefore, a statement claiming “large change of viscosity with temperature” corresponds to a low VI, not a high VI. The flash point apparatus pairings and crude paraffinic K-factor trend are standard facts.
Step-by-Step Solution:a) Pensky–Martens for > 50 °C: aligns with practice.b) Paraffinic crudes having characterisation factor > 12: correct rule of thumb.c) Abel for < 50 °C: correct pairing.d) High susceptibility of viscosity to temperature ≡ low VI, so the statement is wrong.e) Cleveland (open cup) is indeed used for higher flash point materials such as lubricating oils.
Verification / Alternative check:Testing standards and refinery handbooks outline these instrument ranges and the VI definition consistently; laboratory SOPs confirm the above mappings.
Why Other Options Are Wrong (as choices for “incorrect”):a, b, c, e: These reflect accepted practice and definitions.
Common Pitfalls:Reversing the meaning of VI (thinking high VI means large change), or confusing Abel with Pensky–Martens temperature ranges.
Final Answer:An oil that shows a large change of viscosity with temperature has a high viscosity index.