Question 38 QMED03 - Oiler

The Correct Answer is B **Explanation for Option B (Reddish flame) being correct:** In combustion processes, particularly involving hydrocarbon fuels (like natural gas or oil), the color of the flame is an indicator of temperature and the presence of unburned carbon particles. The least complete combustion (lowest efficiency) occurs when there is insufficient oxygen supply. This lack of oxygen results in lower flame temperatures and a high concentration of uncombusted carbon monoxide (CO) and soot (unburned carbon particles). A reddish or deep orange-red flame is characteristic of the lowest temperatures among the choices listed (often indicating temperatures below $1000^{\circ} \text{C}$ or $1800^{\circ} \text{F}$ in industrial viewing), meaning the chemical reaction is the least efficient and thus the **least complete**. A flame that is truly struggling and reddish-brown is essentially choking on fuel and lacks the heat to achieve the brighter colors associated with more complete oxidation. **Explanation for why the other options are incorrect:** * **A) Golden yellow flame:** While a yellow flame indicates the presence of hot soot particles (implying incomplete combustion compared to a blue flame), a golden yellow color is hotter and signifies more complete combustion than a deep reddish or dark orange flame. It is less incomplete than the reddish flame. * **C) Orange flame:** An orange flame (often a bright or vibrant orange) is hotter and indicates a more energetic reaction than a reddish or deep red flame. It represents a moderate level of incomplete combustion, but not the least complete. * **D) Yellow flame:** Similar to the golden yellow flame, a standard yellow flame is hotter and represents more active oxidation than a reddish flame. The red color is at the extreme end of low-temperature combustion visualization, making it the primary indicator of the least complete reaction among the incandescent (soot-based) colors.