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Chemistry > Chemical Tests > Flashcards

Chemical Tests Flashcards

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1
Q

What is the test for hydrogen gas?

A

Squeaky pop test - a lighted splint is held to the mouth of the tube, the hydrogen combines explosively with oxygen in the air to make water.

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2
Q

What is the test for oxygen gas?

A

A glowing splint relights.

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3
Q

What is the test for carbon dioxide gas?

A

If bubbled through limewater, turns cloudy.

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4
Q

What is limewater?

A

Calcium hydroxide solution.

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5
Q

What is the white precipitate formed in limewater from carbon dioxide?

A

Calcium carbonate.

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6
Q

What is the test for chlorine gas?

A

A piece of damp litmus paper or universal indicator paper is put into the test tube or held over its mouth. The chlorine bleaches it (turns white).

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7
Q

What happens if damp blue litmus paper is used in a chlorine gas test?

A

It will go red first before turning white because the chlorine dissolves in the water to form an acidic solution.

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8
Q

What is the test for ammonia, NH3 gas?

A

Hold a piece of damp universal indicator paper or red litmus paper at the mouth of the test tube. Ammonia turns both of these blue.

This is because ammonia is an alkaline gas.

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9
Q

What is the chemical test for water?

A

Water turns anhydrous copper (II) sulfate blue.

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10
Q

What is the difference between cations and anions?

A

Cation = positive ion
Anion = negative ion

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11
Q

What test is used to show the presence of cations (metal ions)?

A

Flame test.

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12
Q

What cation is red under a flame?

A

Lithium ions.

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13
Q

What cation is yellow under a flame?

A

Sodium ions.

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14
Q

What cation is lilac under a flame?

A

Potassium ions.

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15
Q

What cation is orange under a flame?

A

Calcium ions.

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16
Q

What cation is blue-green under a flame?

A

Copper (II) ions.

17
Q

Why can you test for cations using sodium hydroxide solution?

A

Because most metal hydroxides are insoluble, that means if you add sodium hydroxide solution to a solution containing the metal ions, you will get a precipitate of the metal hydroxide.

18
Q

What does blue precipitate show the presence of using sodium hydroxide?

A

Copper (II) ions.

The precipitate is copper (II) hydroxide.

19
Q

What does orange-brown precipitate show the presence of in a cation test using sodium hydroxide?

A

Iron (III) ions.

The precipitate is iron (III) hydroxide

20
Q

What does green precipitate show the presence of using sodium hydroxide?

A

Iron (II) ions.

The precipitate is iron (II) hydroxide.

21
Q

What happens to iron (II) hydroxide precipitate near the surface and why?

A

It darkens and turns orange-brown around the top of the tube due to iron (II) hydroxide being oxidised to iron (III) hydroxide by the air.

22
Q

How can you test to show the presence of an ammonium salt?

A

Sodium hydroxide solution reacts with ammonium salts to produce ammonia gas. In the cold you can smell it, but if warmed, you can test the gas coming off with red litmus paper or universal indicator paper. Both will turn blue as ammonia is alkaline.

23
Q

How do you test for carbonates?

A

Add a little dilute hydrochloric acid to your sample of salt. Fizzing indicates that a gas is given off, bubble this gas through limewater to show that it is carbon dioxide.

24
Q

What state are most carbonates as when used in a carbonate test and why?

A

Solid, as most carbonates are insoluble in water.

25
Q

What is the first thing you do in a sulfate test?

A

Make a solution of suspected sulfate in distilled water.

26
Q

What 2 substances are used to test for sulfates?

A

-Dilute hydrochloric acid
-Barium chloride solution

27
Q

What precipitate is formed in a sulfate test?

A

A white precipitate of barium sulfate.

28
Q

What 2 substances are used when testing for whether a solution is chloride, iodide or bromide.

A

Dilute nitric acid and silver nitrate solution.

29
Q

What precipitate shows the presence of chloride ions?

A

A white precipitate (of silver chloride)

30
Q

What precipitate shows the presence of bromide ions?

A

A cream precipitate (of silver bromide)

31
Q

What precipitate shows the presence of iodide ions?

A

A yellow precipitate (of silver iodide)

32
Q

What do you prepare before carrying out a flame test?

A

Dip a platinum or nichrome wire into dilute hydrochloric acid in then into the salt you want to test.

Chemistry (28 decks)

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