Question

Crude oil denser than pure water has the API gravity

• A. less than \(10^\circ\).
• B. between \(10^\circ\) and \(20^\circ\).
• C. between \(20^\circ\) and \(60^\circ\).
• D. more than \(60^\circ\).

Hint:

API gravity is inversely related to density: higher density (higher SG) \(\Rightarrow\) lower API. Water corresponds to \(10^\circ\) API.

Answer 1

The Correct Option is A

Step 1: Recall the definition of API gravity.
API gravity (in degrees) is defined by \[ {}^\circ\!API \;=\; \frac{141.5}{\text{SG}_{60^\circ\mathrm{F}}} - 131.5, \] where \(\text{SG}_{60^\circ\mathrm{F}}\) is the specific gravity at \(60^\circ\mathrm{F}\). Step 2: Compare with pure water.
Pure water has \(\text{SG}=1\). Substituting, \[ {}^\circ\!API_{\text{water}}=\frac{141.5}{1}-131.5 = 10^\circ. \] Step 3: Heavier (denser) than water \(\Rightarrow \text{SG} > 1\).
The function \(\dfrac{141.5}{\text{SG}} - 131.5\) decreases as SG increases.
Hence, for any crude with \(\text{SG} > 1\), \[ {}^\circ\!API \;=\; \frac{141.5}{\text{SG}} - 131.5 \;<\; \frac{141.5}{1}-131.5 \;=\; 10^\circ. \] (For example, \(\text{SG}=1.05 \Rightarrow {}^\circ\!API \approx 141.5/1.05 - 131.5 \approx 3.2^\circ < 10^\circ\).) Final Answer: \[ \boxed{\text{Less than } 10^\circ} \]