Select the best answer for the question.
Which of these refers to an arbitrary scale devised jointly by the American Petroleum Institute and the National Bureau of Standards that expresses the gravity or
density of liquid petroleum products?
A. Cetane number
B. API gravity
C. Grade number
D. Hydrometer units
The Correct answer and Explanation is:
The best answer is B. API gravity.
Explanation:
API gravity is a measure of the density of liquid petroleum products relative to water, expressed in degrees. The American Petroleum Institute (API) developed this scale, which is widely used in the petroleum industry to determine the density of crude oil and other petroleum products. The API gravity scale is a crucial tool for categorizing different types of petroleum, influencing various aspects of their use, pricing, and refining processes.
API gravity is calculated using the following formula:
[
\text{API gravity} = \frac{(141.5 / \text{Specific Gravity})} – 131.5
]
Where specific gravity is the ratio of the density of the petroleum product to the density of water. If the API gravity is greater than 10, the substance is lighter than water and will float; if it is less than 10, it is heavier and will sink. This distinction is important for various applications, including transportation and storage.
In practice, API gravity is critical for determining the value of crude oil. Higher API gravity typically indicates a lighter oil, which is generally more valuable because it yields a higher percentage of gasoline and other valuable products during refining. Conversely, heavier oils are often less desirable as they require more processing to convert them into usable fuels.
Other options in the question, such as the cetane number (A), which measures the ignition quality of diesel fuel, and grade number (C), which is not a standardized term in this context, do not pertain to the density of petroleum products. Hydrometer units (D) are tools used to measure the specific gravity of liquids but do not represent a standardized scale for petroleum products. Therefore, the most accurate and relevant answer to the question is API gravity (B).