Difficulty: Easy
Correct Answer: Higher flash point and higher fire point
Explanation:
Introduction:Viscosity correlates with molecular weight distribution and volatility in lube oils. Heavier, more viscous oils generally exhibit higher flash/fire points because fewer light, volatile components are present.Given Data / Assumptions:
Concept / Approach:Flash/fire points reflect the temperature at which sufficient vapours form to ignite/sustain combustion. Lower volatility (heavier/viscous oils) requires higher temperatures to produce ignitable vapour concentrations.Step-by-Step Solution:
1) Higher viscosity implies heavier average molecules and lower volatility.2) Lower volatility raises the temperature needed to form flammable vapour.3) Hence, flash and fire points increase with viscosity, all else equal.Verification / Alternative check:Empirical data across lube grades show flash point trending upward with viscosity index/grade, barring additive anomalies.Why Other Options Are Wrong:
Lower flash/fire: opposite of typical trend.Higher acid number: acidity depends on oxidation/contaminants, not viscosity per se.Higher RVP: lube oils have very low RVP; viscosity increase would not raise RVP.Common Pitfalls:Assuming any property increase implies higher reactivity/acidity; viscosity is not a direct measure of acidity.
Final Answer:Higher flash point and higher fire point
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