Photo AI

7 (a) Qualitative tests are carried out on ionic substances to identify the ions present in the substances - Edexcel - GCSE Chemistry - Question 7 - 2019 - Paper 1

Question icon

Question 7

7-(a)-Qualitative-tests-are-carried-out-on-ionic-substances-to-identify-the-ions-present-in-the-substances-Edexcel-GCSE Chemistry-Question 7-2019-Paper 1.png

7 (a) Qualitative tests are carried out on ionic substances to identify the ions present in the substances. (i) Explain why the test for a given ion must be unique ... show full transcript

Worked Solution & Example Answer:7 (a) Qualitative tests are carried out on ionic substances to identify the ions present in the substances - Edexcel - GCSE Chemistry - Question 7 - 2019 - Paper 1

Step 1

Explain why the test for a given ion must be unique to that ion.

96%

114 rated

Answer

The test for a given ion must be unique to that ion to ensure specificity in identifying the presence of that ion without interference from other ions. If a test is not unique, it may produce a false positive result due to the presence of similar ions or compounds, which could lead to incorrect conclusions.

Step 2

State the name of the gas produced in the test if carbonate ions are present.

99%

104 rated

Answer

Carbon dioxide.

Step 3

Draw one straight line from the test for each ion to the observation that shows that ion to be present.

96%

101 rated

Answer

test for chloride ion: → white precipitate test for iodide ion: → yellow precipitate test for sulfate ion: → red precipitate

Step 4

Describe tests to show the presence of each of these metal ions.

98%

120 rated

Answer

  1. Sodium ion (Na⁺): Dissolve the sample in water and perform a flame test. A golden yellow flame indicates the presence of sodium.

  2. Potassium ion (K⁺): Dissolve the sample in water and perform a flame test. A lilac or light purple flame indicates the presence of potassium.

  3. Calcium ion (Ca²⁺): Dissolve the sample in water and add a few drops of dilute sodium hydroxide. A white precipitate forms, indicating the presence of calcium.

  4. Aluminum ion (Al³⁺): Dissolve the sample in water and add a few drops of dilute sodium hydroxide. A white precipitate forms, which dissolves upon adding excess sodium hydroxide, indicating the presence of aluminum.

Join the GCSE students using SimpleStudy...

97% of Students

Report Improved Results

98% of Students

Recommend to friends

100,000+

Students Supported

1 Million+

Questions answered

;