Group 7, the Halogens: Required Practical 4 (includes Group 2) Flashcards

1
Q

Which positive ions do you need to know the tests of?

A
  • Group 2 ions

- Ammonium ions, NH4+

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2
Q

How can you identify group 2 ions?

A
  • Adding sodium hydroxide
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3
Q

Outline the steps of the sodium hydroxide method of testing for group 2 ions

A
  • Add dilute NaOH dropwise to a test tube containing metal solution and observe the precipitate that forms
  • Keep adding NaOH until it’s in excess and record changes
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4
Q

Describe the observation made when magnesium ions, Mg^2+, are added to NaOH and excess NaOH

A

• With OH-
- Slight white precipitate

• With excess OH-
- White precipitate

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5
Q

Describe the observation made when calcium ions, Ca^2+, are added to NaOH and excess NaOH

A

• With OH-
- Slight white precipitate

• With excess OH-
- Slight white precipitate

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6
Q

Describe the observation made when strontium ions, Sr^2+, are added to NaOH and excess NaOH

A

• With OH-
- Slight white precipitate

• With excess OH-
- Slight white precipitate

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7
Q

Describe the observation made when barium ions, Ba^2+, are added to NaOH and excess NaOH

A

• With OH-
- No change

• With excess OH-
- No change

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8
Q

What ions are needed to test for ammonium ions?

A
  • Hydroxide ions, OH-
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9
Q

Outline the steps of the test for ammonium ions

A
  • Add sodium hydroxide solution to solution containing unknown ions
  • Gently heat
  • Hold damp red litmus paper above solution
  • Damp red litmus paper turns blue
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10
Q

What is the positive test result for the test for ammonium ions?

A
  • Damp red litmus paper turns blue
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11
Q

What reaction, including state symbols, occurs between ammonium ions and hydroxide ions during the test for ammonium ions?

A
  • NH4+ (aq) + OH- (aq) → NH3 (g) + H2O (l)
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12
Q

Which negative ions do you need to know the tests of?

A
  • Sulfate ions, SO42-
  • Hydroxide ions, OH-
  • Carbonate ions, CO3^2-
  • Halide ions
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13
Q

Outline the steps of the test for sulfate ions

A
  • Add a little dilute hydrochloric acid
  • Add barium chloride solution, BaCl2
  • White precipitate of barium sulfate forms
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14
Q

What is the positive test result for sulfate ions?

A
  • White precipitate of barium sulfate forms
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15
Q

Why do you need to add hydrochloric acid during the test for sulfate ions?

A
  • To remove any carbonate and sulfite ions

- These would also produce a precipitate

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16
Q

Give the reaction between sulfate ions and barium ions during the sulfate ions test, including state symbols

A
  • Ba^2+ (aq) + SO4^2- (aq) → BaSO4 (s)
17
Q

Outline the steps of the hydroxide ions test

A
  • Add universal indicator or red litmus paper to solution

- Solution or paper turns blue

18
Q

What is the positive result of the hydroxide ion test?

A
  • Solution or paper turns blue
19
Q

Outline the steps of the test for carbonate ions

A
  • Add dilute hydrochloric acid

- Results in effervescence

20
Q

What is the positive result for the carbonate ions test?

A
  • Effervescence
21
Q

Give the reaction between carbonate ions and hydrogen ions during the test for carbonate ions, including state symbols

A
  • CO3^2- (aq) + 2H+ (aq) → CO2 (g) + H2O (l)