ChemistryChapter 18: Qualitative Analysis
Ammonia
Ammonia is a basic gas.
Learning objectives
- State the main idea of ammonia in clear words.
- Explain why ammonia is useful in chemistry.
- Apply the correct method, observation, equation, or comparison.
- Avoid the common mistakes and write a complete exam answer.
Definition
Ammonia is a basic gas. Damp red litmus turns blue. The paper must be damp: the gas needs water to form OH- before the dye can change. Dry litmus shows no change, so the result is uncertain.
Important terms
- basic
- Ammonia is a basic gas.
- damp red litmus
- Ammonia is a basic gas.
- blue
- Ammonia is a basic gas.
- damp
- Ammonia is a basic gas.
- OH-
- Ammonia is a basic gas.
- Dry litmus
- Ammonia is a basic gas.
Overview
How we make it and why it matters:
The Test
Hold damp red litmus in the gas. Blue means alkaline vapour, and in this chapter that points to ammonia. If you forget to dampen the paper, water is missing, OH- does not form, and you must not guess.
Examples Damp red -> blue · Dry paper: no change · Pungent smell (careful)
Haber and Uses
The Haber process joins N2 + H2 on an iron (Fe) catalyst to make ammonia. The main use in the course is fertiliser, because plants need a source of nitrogen they can take up.
Examples N2 + H2 -> ammonia · Fe catalyst in the plant · Fertiliser for crops
WHAT — Core idea
Ammonia is a basic gas. Damp red litmus turns blue. The paper must be damp: the gas needs water to form OH- before the dye can change. Dry litmus shows no change, so the result is uncertain.
WHY — Why it matters
Ammonia is less dense than air and very soluble in water. For identity in Class 9, the damp litmus test is the line to learn, not a long list of extra tricks.
HOW — Method, evidence, or comparison
1. 1. THE TEST: Hold damp red litmus in the gas. Blue means alkaline vapour, and in this chapter that points to ammonia. If you forget to dampen the paper, water is missing, OH- does not form, and you must not guess. 2. 2. HABER AND USES: The Haber process joins N2 + H2 on an iron (Fe) catalyst to make ammonia. The main use in the course is fertiliser, because plants need a source of nitrogen they can take up.
HOW — Answer in an exam
Must be damp. Dry red litmus that stays red is not a fail for ammonia; it is an invalid test. Wet the paper, then watch for blue.
Explanation
Ammonia is less dense than air and very soluble in water. For identity in Class 9, the damp litmus test is the line to learn, not a long list of extra tricks.
In simple words
Must be damp. Dry red litmus that stays red is not a fail for ammonia; it is an invalid test. Wet the paper, then watch for blue.
Key points
- basic
- damp red litmus
- blue
- damp
- Blue
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Ammonia
Sticky Notes · Quick Revision
WHAT
- Ammonia is a basic gas.
Key Points
- basic
- damp red litmus
- blue
- damp
- OH-
HOW
- Hold damp red litmus in the gas.
- The Haber process joins N2 + H2 on an iron (Fe) catalyst to make ammonia.
Example
- Damp red -> blue
- Dry paper: no change
- Pungent smell (careful)
Common Mistake
- The red litmus paper must be damp; dry paper makes the test invalid.
Exam Tip
- Must be damp.
- Dry red litmus that stays red is not a fail for ammonia; it is an invalid test.
60-second revision
- Ammonia is a basic gas.
- Damp red litmus turns blue.
- Hold damp red litmus in the gas.
- The Haber process joins N2 + H2 on an iron (Fe) catalyst to make ammonia.
- Must be damp.
Did you understand this topic?
Your answer is saved with your learning record. It does not mark the topic as mastered.