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Chemistry > Chemical Tests > Flashcards

Chemical Tests Flashcards

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1
Q

Describe the method of conducting a flame test.

A
  1. Dip a piece of nichrome/platinum wire into hydrochloric acid.
  2. Dip the wire into a sample of solid or solution. This causes some of the sample to stick onto the wire.
  3. Place the tip of the wire into a non-luminous Bunsen flame.
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2
Q

Describe the method of conducting a flame test.

A
  1. Dip a piece of nichrome/platinum wire into hydrochloric acid.
  2. Dip the wire into a sample of solid or solution. This causes some of the sample to stick onto the wire.
  3. Place the tip of the wire into a non-luminous Bunsen flame.
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3
Q

What metal cation produces a red flame in a flame test?

A

Lithium

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4
Q

What metal cation produces a yellow flame in a flame test?

A

Sodium (Na)

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5
Q

What metal cation produces a lilac flame in a flame test?

A

Potassium

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6
Q

What metal cation produces an orange-red flame in a flame test?

A

Calcium

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7
Q

What metal cation produces a blue-green flame in a flame test?

A

Copper

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8
Q

Describe the test for cations using sodium hydroxide solution.

A

Dissolve the salt in distilled water and put about 1cm3 in a test tube. The solution will go cloudy as a solid forms.

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9
Q

What is the colour of the precipitate of copper hydroxide?

A

Blue

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10
Q

What is the colour of the precipitate of iron (II) hydroxide?

A

Green

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11
Q

What is the colour of the precipitate of iron (III) hydroxide?

A

Brown

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12
Q

Describe the method of conducting an ammonium test.

A

Dissolve the sample in water
Add some NaOH (aq)
Test the gas evolved with damp red litmus paper.
If NH4 + ions are present in the original sample the litmus paper will turn blue.

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13
Q

Describe the test for halide ions using the silver nitrate test.

A

Dissolve the sample in water
Add nitric acid (HNO3)
Add silver nitrate (AgNO3) solution
If Cl-, Br-, I- ions are present, a precipitate forms.

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14
Q

What precipitate has a white colour?

A

AgCl

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15
Q

What precipitate has a cream colour?

A

AgBr

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16
Q

What precipitate has a yellow colour?

A

AgI

17
Q

Why is it important to add Nitric acid into the silver nitrate test?

A

Because silver ions also form precipitates with other anions like hydroxide and carbonate. The nitric acid reacts with those anions preventing false positives.

18
Q

Describe the method of a test for carbonates.

A

Add hydrochloric acid, look for effervescence.
If there is effervescence, bubble the gas through limewater.
If CO3 2- ions were present in the sample, the has evolved turns into limewater cloudy.

19
Q

Why is platinum a suitable metal to use as the wire in a flame test?

A

It has a high melting point
It doesn’t effect the colour of the flame

Chemistry (16 decks)

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