Fuel rating basics: In the octane number scale used for gasoline, what value is assigned to normal heptane (n-heptane)?
-
A0
-
B70
-
C100
-
DInfinity
Answer
Correct Answer: 0
Explanation
Introduction / Context:Octane number quantifies the knock resistance of gasoline in spark-ignition engines. It is defined by comparing a test fuel to a blend of iso-octane and n-heptane under standardized conditions.
Given Data / Assumptions:
- Reference fuels: iso-octane and n-heptane.
- Scale anchors: iso-octane set high, n-heptane set low.
- Measurement methods: RON and MON (principles similar for the scale reference).
Concept / Approach:By definition, iso-octane is assigned octane number 100 as the high-knock-resistance reference, and n-heptane is assigned octane number 0 as the low-resistance reference. Real fuels are compared to equivalent blends between these anchors.
Step-by-Step Solution:
Step 1: Recall scale endpoints: iso-octane = 100, n-heptane = 0.Step 2: Select the assigned value for n-heptane = 0.Step 3: Confirm that other values are distractors.Verification / Alternative check:Standard fuel testing handbooks and ASTM methods state the same scale definition.
Why Other Options Are Wrong:
- 100: Assigned to iso-octane, not n-heptane.
- 70: Arbitrary; not a reference endpoint.
- Infinity: Not used in octane scaling.
Common Pitfalls:Confusing cetane scale (diesel ignition quality) with octane; they are opposite in their performance meaning.
Final Answer:0