Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Chemical Tests
68 practice questions
Topics covered
Practice questions
11–20 of 68
Question 11
3 marks · Normal
Answer and see the solution →A sample of gas in a test-tube is suspected to be ammonia. A student tests this gas using damp red litmus paper. He repeats the test with chlorine gas for comparison.
(a)[1 mark]State the result when ammonia gas is tested with damp red litmus paper.
(b)[1 mark]State the result when chlorine gas is tested with damp red litmus paper.
(c)[1 mark]Explain how these tests can be used to identify ammonia gas in a mixture of alkaline and acidic gases.
Question 12
3 marks · Normal
Answer and see the solution →A student tests two samples, A and B, for water. Both samples turn white anhydrous copper(II) sulfate blue. When heated, sample A boils at 102°C and sample B boils at 100°C (at 1 atm pressure).
Explain, with reasons, which sample is pure water and which is not.
Question 13
4 marks · Normal
Answer and see the solution →A student is given a colourless liquid and asked to determine if it is pure water. The student has access to anhydrous copper(II) sulfate, a thermometer, a beaker, and a Bunsen burner.
(a)[2 marks]Describe how the student could use anhydrous copper(II) sulfate to test whether the liquid contains water.
(b)[1 mark]State the colour change that would be seen if water is present.
(c)[1 mark]Describe how the student can use a thermometer and a Bunsen burner to test if the water is pure.
Question 14
3 marks · Normal
Answer and see the solution →A student measures the volume of a gas collected during a chemical reaction. She suspects it is ammonia. The laboratory temperature is 22°C and the gas is bubbled through 20 cm³ of water. The final pH of the water is found to be 12.2. Pure water has a pH of 7.0.
By how many units did the pH of the water increase? What does this pH reading suggest about the nature of the gas?
Question 15
3 marks · Normal
Answer and see the solution →Water found in a river is tested using anhydrous copper(II) sulfate. The solid turns blue. Explain why this test does not prove the water is pure, and suggest a further test to check its purity.
Question 16
4 marks · Normal
Answer and see the solution →A teacher tests four gases (W, X, Y, Z) using both damp red litmus paper and universal indicator paper. The results are shown.
Colour change results of gas tests Gas Red litmus paper Universal indicator paper W No change No change X Turns blue Turns blue Y No change Turns red Z Bleaches Bleaches (a)[2 marks]Which gas (W, X, Y, or Z) is most likely to be ammonia? Explain your answer.
(b)[2 marks]Suggest the identity of one other gas (Y or Z), giving a reason.
Question 17
2 marks · Normal
Answer and see the solution →A student is given a sample of gas and uses a piece of damp red litmus paper to test it.
State the result if the gas is ammonia. Explain why this result is seen.
Question 18
2 marks · Hard
Answer and see the solution →A colourless liquid is suspected to contain water, but may also have dissolved salts. You are given a thermometer and a Bunsen burner. State how you would use these to test for the purity of the water and describe what result confirms that it is pure.
Question 19
5 marks · Hard
Answer and see the solution →A student is given three unknown gases: Gas A, Gas B, and Gas C. She is told that one may be ammonia, another is hydrogen, and the third is chlorine. She uses damp red litmus paper to test each gas.
(a)[1 mark]State what is observed when damp red litmus paper is placed in ammonia gas.
(b)[1 mark]Describe what happens to damp red litmus paper when it is exposed to chlorine gas.
(c)[2 marks]Explain why ammonia is the only alkaline gas among the three.
(d)[1 mark]Suggest an additional chemical test to identify hydrogen, apart from using litmus paper. State what result confirms hydrogen is present.
Question 20
2 marks · Hard
Answer and see the solution →A student performs a test for water using anhydrous copper(II) sulfate. The white powder turns blue when a sample liquid is added. State what this test does and does not show about the sample.