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Chemistry > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

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1
Q

How do you test for hydrogen? What is the positive test?

A

Place a lit splint over a test tube of gas. Positive test: the hydrogen burns rapidly and makes a ‘squeaky pop’ sound.

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2
Q

How do you test for oxygen? What is the positive test?

A

Insert a glowing splint into a test tube. Positive test: the glowing splint relights.

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3
Q

How do you test for carbon dioxide? What is the positive test?

A

Bubble the gas through limewater. Positive test: the limewater turns milky/cloudy.

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4
Q

How do you test for chlorine? What is the positive test?

A

Hold a piece of damp blue litmus paper over the test tube. Positive test: the litmus paper is bleached and turns white.

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5
Q

How do you test positive ions?

A

There are two methods:

  • Flame test
  • Sodium hydroxide test
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6
Q

How do you test for Na+?

A

Flame test: Yellow.

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7
Q

How do you test for Ca2+?

A

Flame test: Orange/Red.

Sodium hydroxide: White precipitate.

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8
Q

How do you test for Li+?

A

Flame test: Crimson.

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9
Q

How do you test for K+?

A

Flame test: Lilac/Violet.

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10
Q

How do you test for Mg2+?

A

Sodium hydroxide: White precipitate.

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11
Q

How do you test for Cu2+?

A

Flame test: Green.

Sodium hydroxide: Blue precipitate.

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12
Q

How do you test for Fe2+?

A

Sodium hydroxide: Green precipitate.

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13
Q

How do you test for Fe3+?

A

Sodium hydroxide: Brown/Red precipitate.

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14
Q

How do you test for Al3+?

A

Sodium hydroxide: White precipitate.

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15
Q

How do you test for negative ions?

A

There are three ways:

  • For carbonates: Add dilute hydrochloric acid to see if it fizzes. Then test it with limewater. If it fizzes with the acid and turns limewater cloudy, carbonate ions are present.
  • For halides: Add dilute nitric acid and silver nitrate solution. A precipitate is formed when halide ions are present.
  • For sulfates: Add dilute hydrochloric acid and barium chloride solution. A white precipitate forms if sulfate ions are present.
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16
Q

How do you test for Cl-?

A

Nitric acid + silver nitrate: Cloudy/White precipitate.

17
Q

How do you test for SO4, 2-?

A

Nitric acid + silver nitrate: Cloudy/Milky precipitate.

18
Q

How do you test for F-?

A

Nitric acid + silver nitrate: No precipitate.

19
Q

How do you test for I-?

A

Nitric acid + silver nitrate: Yellow precipitate.

20
Q

How do you test for Br-?

A

Nitric acid + silver nitrate: Creamy precipitate.

21
Q

How do you test for CO3, 2-?

A

HCl + Limewater: A fizz in acid and cloudy limewater.

22
Q

What is flame emission spectroscopy?

A

It is an instrumental analysis method which is used to analyse samples from metal ions. When the sample is heated in a flame, the light produced is analysed. Each metal ion has its own characteristic pattern, called its line spectrum. You can identify the metal ions present through this.

23
Q

How does flame emission spectroscopy work?

A

Low energy shell electrons gain energy and move to the outer shells. Here, they then lose energy and move back again. Light is emitted through this.

24
Q

How do you work out the rf value on a chromatography?

A

Distance moved by substance / Distance moved by solvent

OR

Small number / big number

25
Q

How do you test if a substance is pure?

A

By analysing it’s boiling point. If it has one boiling point, it is pure. If it has multiple, it means it is made up for more than one compound.

26
Q

How is the solvent front distance measured?

A

From the bottom of the paper to the solvent front.

27
Q

What is the solvent in chromatography?

A

Water.

28
Q

What does a substance higher up the paper in chromatography mean?

A

It is more soluble.

Chemistry (19 decks)

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