🔍 Key Concepts

• Anhydrous ammonia properties – how it behaves when it leaks, and what you normally see in air. • Sulphur candle reaction – what happens when sulphur (sulfur) burns and its combustion products mix with ammonia. • Visual indicators of leaks – why certain gases are detected by color changes or smoke appearance.

💭 Think About

• Think about what color a normal anhydrous ammonia leak appears as in air before adding any chemicals. • Consider what burning sulphur typically looks like and what color smoke it gives off on its own, without ammonia present. • Ask yourself whether the purpose of using a sulphur candle is to create a distinctly different color from the usual appearance of an ammonia leak so it is easier to see. What color contrast would make sense?

✅ Before You Answer

• Be clear on the natural appearance of ammonia vapors in air (with no sulphur candle). • Recall the typical color of smoke from burning sulphur alone and how that might change when it reacts with another chemical. • Choose the option that gives a clear, easily visible contrast compared to what you would normally see from an ammonia leak without any aid.