Ammonia, NH3 / The test for ammonia gas
3 marks · EasyDescribe the steps for testing a sample for ammonia gas using litmus paper.
Explain why the litmus paper must be damp.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Hold a piece of damp red litmus paper at the mouth of the test-tube containing the gas. If ammonia is present, the litmus turns blue.
(b) The litmus paper must be damp so that ammonia gas can dissolve in the water and react.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Mentions using red litmus paper at the mouth of the test-tube.
B1 (a) · 1 mark · States that ammonia turns it blue.
B1 (b) · 1 mark · Explains that the litmus must be damp so ammonia can dissolve and react.
Worked solution
(a) Hold damp red litmus paper at the mouth of the test-tube with the gas. Ammonia will turn the litmus paper blue.
(b) The litmus paper must be damp so ammonia gas can dissolve and affect the litmus dye.