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a-level oxford chem > Test for Ions > Flashcards

Test for Ions Flashcards

1
Q

Name the 2 tests for Group 2 ions

A
  • Dilute sodium hydroxide
  • Dilute sulfuric acid
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2
Q

Test for Group 2 Ions

Describe what you would do using dilute sodium hydroxide

A
  1. Add 10 drops of barium chloride in test tube
  2. Add 10 drops of sodium hydroxide in test tube & mix well
  3. Add sodium hydroxide, dropwise, until in excess
    • Test tube shouldn’t be more than half-way full
  4. Repeat this test with calcium bromide, magnesium chloride and strontium chloride
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3
Q

Test for Group 2 Ions

Describe what you would do using dilute sulfuric acid

A
  1. Place about 10 drops of barium chloride in test tube
  2. Add 10 drops of sulfuric acid in test tube & mix well
  3. Add sulfuric acid, dropwise, until in excess
    • Test tube shouldn’t be more than half-way full
  4. Repeat this test with calcium bromide, magnesium chloride and strontium chloride
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4
Q

Test for Group 2 Ions

Results when using dilute sodium hydroxide: fill in the blanks

A
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5
Q

Describe the test for ammonia gas

A
  • Ammonia gas is alkaline
  • Can test for it using damp piece of red litmus paper
  • If ammonia present = paper turns blue
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6
Q

Testing for Ammonia

Why does red litmus paper have to be damp?

A

So ammonia gas can dissolve

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7
Q

If you add hydroxide ions to solution containing ammonium ions (NH4+), what it produce?

A

ammonia gas and water

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8
Q

Write an equation to show the reaction between hydroxide ions and ammonium ions

A
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9
Q

Describe the test for ammonium ions

A
  1. Add dilute sodium hydroxide solution to unknown substance in test tube & gently heat mixture
  2. If ammonia given off = ammonium ions must be present
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10
Q

Write the equation for the test for sulfate ions

A
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11
Q

Hydroxide ions make solution ____

A

alkaline

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12
Q

Describe the test for hydroxide ions

A
  1. Dip piece of red litmus paper into solution
  2. If hydroxide ions present = paper turns blue
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13
Q

Describe the test for carbonate ions (CO32-)

A
  1. Add dilute hydrochloric acid = solution with carbonate ions will fizz
  2. Bubble gas (CO2) through test tube of limewater and watch what happens
  3. Limewater = cloudy = carbonate ions in solution
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14
Q

Why is that when you add dilute hydrochloric acid to a solution with carbonate ions, it will fizz?

A

∵ carbonate ions react with hydrogen ions in acid to give carbon dioxide

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15
Q

Write the equation of carbonate ions reacting with hydrogen ions

A
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16
Q

Test for Group 2 Ions

Results when using dilute sulfuric acid: fill in the blanks

17
Q

Describe the test for halide ions in solid salts using
concentrated sulfuric acid

A
  1. Add small amount of solid potassium chloride in test tube
  2. Add few (2 to 5) drops of concentrated sulfuric acid
  3. Test gas produced with moist blue litmus paper
    • Make sure litmus paper doesn’t touch side of tube
  4. Repeat experiment with solid potassium bromide
    • Test gas produced using strip of filter paper dipped in acidified potassium dichromate solution
  5. Repeat experiment with solid potassium iodide
    • Test gas produced using strip of filter paper dipped in lead nitrate solution
18
Q

Name 2 safety procedures when testing for halide ions in solid salts using concentrated sulfuric acid

A
  • Gloves must be worn
  • Must be done in fume cupboard
19
Q

State the results of when potassium chloride reacts with concentrated sulfuric acid. Include the paper result.

20
Q

State the results of when potassium bromide reacts with concentrated sulfuric acid. Include the paper result.

21
Q

State the results of when potassium iodide reacts with concentrated sulfuric acid. Include the paper result.

22
Q

Describe the test for sulfate ions (SO42-)

A
  1. Add dilute hydrochloric acid and then barium chloride solution, BaCl2(aq)
  2. If white precipitate of barium sulfate forms = original compound contained sulfate
23
Q

Test for sulfate ions

Why should you acidify the solution?

A

To get rid of any lurking sulfites or carbonates which will also produce a white precipitate

24
Q

Describe the test for halides

A
  1. Add dilute nitric acid (HNO3) and then silver nitrate solution (AgNO3)
  2. Precipitate is formed (of silver halide)
25
Q

Test for Halides

What is the result for fluoride?

A

No precipitate

26
Q

Test for Halides

What is the result for chloride?

A

White precipitate of silver chloride

27
Q

Test for Halides

What is the result for bromide?

A

Cream precipitate of silver bromide

28
Q

Test for Halides

What is the result for iodide?

A

Yellow precipitate of silver iodide

29
Q

Test for Halides

What can you do to be sure of your results & why does this work?

A
  • You can test your results by adding ammonia solution
  • Each silver halide has a different solubility in ammonia
30
Q

Test for Halides

Write the general equation

31
Q

Fill in the gaps (speed)

32
Q

Fill in the gaps

33
Q

Test for Halides

Why do you add dilute nitric acid?

A

To remove ions which may interfere with test

a-level oxford chem (34 decks)

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