AQA GCSE Chemistry Foundation (8462), Foundation tier · Chemical analysis › Identification of common gases
Practise Test for hydrogen. 8 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
How to show that a gas is hydrogen: a burning splint held at the mouth of the tube gives a squeaky pop. Usually a 2-mark 'describe a test and give the result' question, sometimes linked to reactions that make hydrogen.
Key facts
Test: burning splint held at the open end of a test tube of the gas
Result: hydrogen burns rapidly with a (squeaky) pop
metal + acid → salt + hydrogen
reactive metal + water → metal hydroxide + hydrogen
Burning splint = hydrogen test; glowing splint = oxygen test
Notes
The test
diagram
Collect the gas in a test tube.
Hold a burning splint at the open end (mouth) of the test tube.
If the gas is hydrogen, it burns rapidly with a pop sound (a 'squeaky pop').
Hydrogen: burning splint held at the mouth of the tube, squeaky pop.
Hydrogen is much less dense than air and escapes quickly, so keep the tube stoppered until you test it.
Where hydrogen comes from
Metals such as magnesium and zinc react with dilute acids to form a salt and hydrogen, e.g. magnesium + hydrochloric acid → magnesium chloride + hydrogen.
Very reactive metals, such as sodium and lithium, react with water to form a metal hydroxide and hydrogen.
In the electrolysis of many solutions, such as sodium chloride solution, hydrogen forms at the negative electrode (cathode).
A burning splint going out does not identify a gas: many gases put out a flame.
How to answer each type of question
Describe the test for hydrogen and give the result
2 marksGrade 3
Test (1 mark): a burning splint held at the open end of the tube.
Result (1 mark): a (squeaky) pop.
Example. A student adds zinc to dilute sulfuric acid. Bubbles of gas are produced. Describe a test to show that the gas is hydrogen. Give the result of the test.
Show the model answerHide the model answer
Hold a burning splint at the open end of a test tube of the gas (1). The gas burns with a (squeaky) pop (1).
Identify the gas and complete an equation
1 to 3 marksGrade 5
Look at the reactants: a metal with an acid, or a reactive metal with water, gives hydrogen.
Use the test result given: a pop with a burning splint means hydrogen.
For metal + water, the other product is the metal hydroxide; for metal + acid, it is a salt.
Example. A small piece of lithium is added to water. It fizzes. A burning splint held at the mouth of a tube of the gas gives a squeaky pop. (a) Name the gas. (b) Complete the word equation: lithium + water → .................... + ....................
Using a glowing splint: that is the test for oxygen.
Putting the splint into the liquid. Hold it at the open end of a test tube of the gas.
Writing 'it makes a noise' or 'it explodes'. Write 'pop' or 'squeaky pop'.
Giving 'the splint goes out' as the result for hydrogen.
Writing H instead of H2 for hydrogen gas in an equation.
More tips
Memory tricks
Hydrogen is the gas that burns, so it gets the burning splint. Oxygen helps things burn, so it brings a glowing splint back to life.
'H for Hydrogen, P for Pop': hydrogen pops.
'MASH': Metal + Acid → Salt + Hydrogen.
Exam technique
Two marks = test + result: 'burning splint' and 'pop'.
Learn the four gas tests as a set, because questions often ask you to choose between them.
If a question asks how you know a gas is hydrogen, give the test result, not just the reaction that made it.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Describe the test for hydrogenHold a burning splint at the open end of a test tube of the gas.
Grade 3
State the positive result for hydrogenHydrogen burns rapidly with a pop sound (a 'squeaky pop').
Grade 4
Tell the hydrogen and oxygen tests apartHydrogen: burning splint gives a pop. Oxygen: glowing splint relights.
Grade 5
Name reactions that produce hydrogenMetals with acids, very reactive metals with water, and electrolysis of many solutions (at the negative electrode).
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Name the product of the reaction between hydrogen and oxygen.
water
The squeaky pop happens because hydrogen reacts very quickly with oxygen in the air. Name the product of this reaction.
water
A student adds excess magnesium ribbon to dilute sulfuric acid in a conical flask fitted with a delivery tube, and collects the gas produced over water in an upturned test tube. Name the salt produced in this reaction.
magnesium sulfate
Complete the word equation for the reaction. zinc + hydrochloric acid → .................... + hydrogen
zinc chloride
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy3 marks
A student added magnesium ribbon to dilute hydrochloric acid in a test tube. A gas was produced.
(a) Give one observation that would show a gas is being produced.[1]
(b) The gas was hydrogen. Describe the test for hydrogen and give the result.[2]
Show the answer and mark scheme
(a)
bubbles / fizzing / effervescence
(b)
(hold a) burning / lit splint at the open end of the test tube
(the hydrogen burns rapidly with a) (squeaky) pop
Question 2Medium4 marks
Hydrogen can react rapidly with oxygen from the air. The reaction makes a squeaky pop.
(a) Name the product of the reaction between hydrogen and oxygen.[1]
(b) Balance the equation for the reaction. ....H2 + ....O2 → ....H2O[1]
(c) A student collected a test tube of an unknown gas and put a glowing splint into it. The splint did not relight. The student concluded that the gas was hydrogen. Explain why the student’s conclusion is not valid.[2]
Show the answer and mark scheme
(a)Answer: water
water / water vapour / steam
(b)Answer: 2H2 + O2 → 2H2O
2H2 + O2 → 2H2O
(c)
a glowing splint is the test for oxygen / only shows that the gas is not oxygen
to show the gas is hydrogen, hold a burning splint at the mouth of the tube and listen for a (squeaky) pop