Test for cations Flashcards

1
Q

What happens when aqueous sodium hydroxide is added to Ammonium?

A

No ppt. formed, solution remains colourless (same for aqueous ammonia).
On warming, a colourless and pungent gas is evolved.
Gas evolved turns moist red litmus paper blue.

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2
Q

Which four cations form white ppt. when aqueous sodium hydroxide is added?

A
  1. Calcium
  2. Aluminium
  3. Lead
  4. Zinc
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3
Q

Which one of the following cations, Calcium, Aluminium, Lead, and Zinc forms white ppt. that is insoluble in excess aqueous sodium hydroxide?

A

Calcium

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4
Q

Does calcium form ppt. when aqueous ammonia is added?

A

No ppt. is formed, solution remains colourless.

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5
Q

Which one of the three cations that form white ppt. when aqueous ammonia is added forms white ppt. that is soluble in excess aqueous ammonia to form a colourless solution?

A

Zinc

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6
Q

What colour ppt. does Copper (II) cation form when both aqueous sodium hydroxide and aqueous ammonia is added?

A

Light blue ppt.

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7
Q

What colour ppt. does Iron (II) cation and Iron (III) cation form respectively?

A

Green ppt. and Reddish-brown ppt.
(Both insoluble in excess aqueous sodium hydroxide and aqueous ammonia)

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8
Q

When excess aqueous sodium hydroxide is added to Copper (II) cation, is the light blue ppt. soluble or insoluble?

A

Light blue ppt. insoluble in excess aqueous sodium hydroxide.
Light blue ppt. turns black on heating

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9
Q

When excess aqueous ammonia is added to Copper (II) cation, is the light blue ppt. soluble or insoluble?

A

Light blue ppt. soluble in excess aqueous ammonia to give a deep blue solution

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10
Q

What are the three tests to differentiate between Lead and Aluminium cations?

A
  1. Add aqueous potassium iodide
  2. Add dilute sulfuric acid
  3. Add dilute hydrochloric acid
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11
Q

What are the observations for aqueous potassium iodide test?
(Differentiating between Lead and Aluminium cation)

A
  1. Yellow ppt. forms if Lead cation is present.
  2. No ppt forms, solution remains colourless if Aluminium cation is present.
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12
Q

What are the observations for dilute sulfuric acid test?
(Differentiating between Lead and Aluminium cation)

A
  1. White ppt. forms if Lead cation is present.
  2. No ppt forms, solution remains colourless if Aluminium cation is present.
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13
Q

What are the observations for dilute hydrochloric acid test?
(Differentiating between Lead and Aluminium cation)

A
  1. White ppt. forms if Lead cation is present.
  2. No ppt forms, solution remains colourless if Aluminium cation is present.
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