Chemical tests

Question 1

Describe the test for hydrogen gas?

Answer 1

Burnt splint test - hydrogen gas will ignite with a squeaky pop sound

Question 2

Describe the test for oxygen gas?

Answer 2

A good method to test for oxygen is to take a glowing splint and place it in a sample of gas, if it re-ignites the gas is oxygen.

Question 3

Describe the test for carbon dioxide?

Answer 3

Carbon dioxide turns lime water cloudy/milky

Question 4

Describe the test for ammonia gas?

Answer 4

• It will turn moist litmus paper from red to blue.

- Ammonia gas will put out a lit splint

Question 5

Describe the test for chlorine gas?

Answer 5

The simplest test for chlorine is a litmus paper test, chlorine will turn a damp blue litmus paper red, and then it’ll bleach it white

Question 6

How do you carry out a flame test?

Answer 6

1-dip a clean wire loop into a solid sample of the compound being tested.
2-put the loop into the edge of the blue flame from a Bunsen burner.
3-observe and record the flame colour produced.

Question 7

Flame test for Li+

Answer 7

Red

Question 8

Flame test for Na+

Answer 8

Yellow

Question 9

Flame test for K+

Answer 9

Lilac

Question 10

Flame test for Ca2+

Answer 10

Orange-red

Question 11

Flame test for Cu2+

Answer 11

blue-green

Question 12

Test for NH4+ ammonia using sodium hydroxide

Answer 12

METHOD:
-Add Aqueous Sodium Hydroxide to the solid or solution and heat using Bunsen burner
-Lower damp red litmus paper into gas produced
RESULT:
If Ammonium ions are present, pungent-smelling gas is produced
Gas produced turns damp red litmus paper Blue

Question 13

Test for Cu2+

Answer 13

Step 1: some solution is poured in a test tube.
Step 2: A few drops of an aqueous solution of sodium hydroxide (which acts as a reactive) are added.
Step 3: A blue precipitate forms which confirms the presence of copper ions.

Question 14

Test for Fe2+

Answer 14

Add a few drops of sodium hydroxide solution to the solution. A dirty-green precipitate forms

Question 15

Test for Fe3+

Answer 15

Add a few drops of sodium hydroxide solution to the solution. A reddish-brown precipitate forms

Question 16

Test for Chloride, Bromide and Iodide Ions using silver nitrate solution

Answer 16

Add a few drops silver nitrate solution to the solutions containing either Cl, Br or I ions.
Cl - white precipitate
Br - very pale cream precipitate
I - very pale yellow precipitate

Question 17

Test for SO4-2

Answer 17

The test solution is acidified using a few drops of dilute hydrochloric acid, and then a few drops of barium chloride solution are added. A white precipitate of barium sulfate forms if sulfate ions are present.

Question 18

Test for C03-2

Answer 18

Carbonate ions, CO3 2- are detected using a dilute acid . Bubbles are given off when an acid, usually dilute hydrochloric acid, is added to the test compound . The bubbles are caused by carbon dioxide. Limewater is used to confirm that the gas is carbon dioxide.

Question 19

Describe the test for the presence of water using anhydrous copper(II) sulfate

Answer 19

The white solid turns blue in the presence of water

Question 20

Describe a physical test to show whether a sample of water is pure

Answer 20

If the sample is pure water it will boil at 100 degrees