Separating mixtures

Question 1

What apparatus do you need to test for hydrogen gas?

Answer 1

• Test tube of dilute hydrochloric acid and zinc
• Boiling tube
• Splint
• Bunsen burner

Question 2

What safety precautions do you need to take when testing for hydrogen?

Answer 2

Wear eye protection. Hydrogen gas is flammable.

Question 3

What steps need to be taken when testing for hydrogen?

Answer 3

1. Record your observations when you hold a lighted splint at the open end of the test tube of hydrogen gas.
2. Explain your observations.
3. What do the methods of collecting hydrogen gas tell you about its properties?

Question 4

What observation will we make for a positive test for hydrogen?

Answer 4

A lighted splint ‘pops’

Question 5

What steps need to be taken to test for oxygen?

Answer 5

1. Collect 15cm*3 hydrogen peroxide solution in a small conical flask.
2. Add a small amount of manganese oxide from the end of a spatula.
3. Insert a glowing splint (made by blowing out a lighted splint) in the mouth of the flask.
4. Record and explain your observations.

Question 6

What safety precautions do we need to take when testing for oxygen?

Answer 6

Wear eye protection

Question 7

What observation will we make if oxygen is present?

Answer 7

A glowing splint relights

Question 8

What is the hydrogen test called?

Answer 8

Squeaky pop test.

Question 9

What is the oxygen test called?

Answer 9

Relighting splint test

Question 10

What is the carbon dioxide test called?

Answer 10

Limewater test

Question 11

What apparatus do you need to test for carbon dioxide?

Answer 11

• Marble chips
• Dilute hydrochloric acid
• Limewater
• Test tube with cork and glass tube
• Another test tube

Question 12

What is the objective of the limewater test?

Answer 12

To bubble carbon dioxide gas through limewater (calcium hydroxide solution) using the apparatus.

Question 13

What observation will we make if carbon dioxide is present?

Answer 13

The limewater turns milky (cloudy white)

Question 14

What type of gas is chlorine?

Answer 14

A toxic gas

Question 15

What are the steps taken to test for chlorine gas?

Answer 15

1. Concentrated hydrochloric acid (corrosive) will be added to a spatula of moistened potassium manganate crystals in a boiling tube held in a rack inside a fume cupboard.
2. A piece of damp blue litmus paper can be held in
   the mouth of the boiling tube.

Question 16

What observation will we make if chlorine gas is present.

Answer 16

The damp blue litmus paper turns white (as it gets bleached)

Question 17

What are the steps to separating substances using chromatography?

Answer 17

1. Prepare the paper by drawing a pencil line across the paper near to the bottom.
2. Place a small dot of each permanent and non-permanent felt tip pen on the line.
3. Add a small amount of solvent (in this case water) to a beaker and the paper suspended so water level is BELOW the line on the paper.

As the water rises up the paper, the substance are carried up the paper. The different components in the mixtures move at different rates and are separated out.

4. Measure the distance moved by the solvent and the distances moved by each colour. Measure from the starting line to the centre of the colour. Calculate the Rf value for each colour.

Retention factor = distance moved by substance / distance moved by solvent

Question 18

Distillation is a method of ________ liquids.

Answer 18

purifying

Question 19

What happens during the distillation of ink?

Answer 19

Ink consists of a coloured substances dissolved in water. When the ink is boiled the water turns to steam and condenses in the test tube. The coloured substances remain in the flask.

A few anti-bumping granules are placed in the flask to ensure smooth boiling.