Question

What will be the gravity of a petroleum product in API scale if its specific gravity at \(15^\circ\text{C}\) is 0.99?

• A. Equal to 1
• B. Equal to 10
• C. More than 10
• D. Less than 10

Hint:

Rule of thumb:
If $\text{SG} < 1.0$ (lighter than water) $\implies {}^\circ\text{API} > 10$.
If $\text{SG} = 1.0$ (water) $\implies {}^\circ\text{API} = 10$.
If $\text{SG} > 1.0$ (heavier than water) $\implies {}^\circ\text{API} < 10$.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The American Petroleum Institute (API) gravity is an inverse measure of the relative density of a petroleum liquid compared to water.
Key Formula or Approach:
\[ ^\circ\text{API} = \frac{141.5}{\text{Specific Gravity at } 60^\circ\text{F } (15.56^\circ\text{C})} - 131.5 \]

Step 2: Detailed Explanation:
For pure water with specific gravity \(\text{SG} = 1.0\):
\[ ^\circ\text{API} = \frac{141.5}{1.0} - 131.5 = 10.0 \]
For the given petroleum product with \(\text{SG} = 0.99\):
\[ ^\circ\text{API} = \frac{141.5}{0.99} - 131.5 \approx 142.93 - 131.5 = 11.43 \]
Since \(11.43 > 10\), the API gravity of the product is greater than 10.

Step 3: Final Answer:
Thus, the API gravity is more than 10, matching option (C).