STUDENT SPACE · TOPIC 1

Hydrogen and ammonia

Use gas tests and explain the reaction of ammonium ions with alkali.

The essentials

Hydrogen is H₂, an element. A lighted splint gives a squeaky pop with hydrogen.
NH₃ is an uncharged molecule. NH₄⁺ is a positively charged ion found in ammonium salts.
Warming an ammonium salt with aqueous sodium hydroxide releases ammonia.

Try each question before opening its hint or answer. Use paper for calculations and diagrams.

Why must litmus paper be damp when testing ammonia?

Need a hint for Question 1?

Separate the gas molecule from the ion in solution. Identify a reagent, observation and conclusion.

Check Question 1

Ammonia dissolves in the water and produces an alkaline solution that changes the indicator colour.

State a positive test for hydrogen and for ammonia.

Need a hint for Question 2?

State both the test method and its positive observation.

Check Question 2

Hydrogen gives a squeaky pop with a lighted splint. Ammonia turns damp red litmus blue.

Complete and balance NH₄⁺ + OH⁻ → ... and explain the difference between NH₃ and NH₄⁺.

Need a hint for Question 3?

Balance nitrogen, hydrogen, oxygen and overall charge.

Check Question 3

NH₄⁺ + OH⁻ → NH₃ + H₂O. NH₃ is an uncharged molecule; NH₄⁺ is a positive ion.

Use Lesson 1 in your worksheet for written practice. Your teacher will discuss those answers in class.