Topic 8 - Chemical analysis

Question 1

What does pure substance mean?

Answer 1

Something which contained only 1 compound or element throughout it.

Question 2

How do we test if a substance is pure?

Answer 2

1. Measure the substances boiling/melting point
2. Compare it to a known pure substance
3. The closer your measured value to the actual melting/boiling point, the purer substance is

Question 3

What do impurities in a substance do to it’s melting/boiling point?

Answer 3

1. Impurities in the sample lower the melting point, and increase the melting range
2. It will also increase the boiling point and may result in the substance boiling at a range of temps.

Question 4

What are formulations?

Answer 4

Useful mixtures with a precise purpose, which are made by following a formula. Each component of the formulation contributes so that the formulation meets its required function

Question 5

What industry are formulations often used in?

Answer 5

The pharmaceutical industry.

Question 6

What are the 2 phases in chromatography?

Answer 6

1. Mobile phase - where the molecules can move
2. Stationary phase - where the molecules can’t move.

Question 7

How do we calculate the Rf value?

Answer 7

Distance travelled by substance/distance travelled by solvent

Question 8

What is the test for chlorine?

Answer 8

Chlorine bleached damp litmus paper, turning it white.

Question 9

What is the test for oxygen?

Answer 9

Put a glowing splint inside a test tube containing oxygen, the oxygen will relight the glowing splint.

Question 10

What is the test for carbon dioxide?

Answer 10

Bubbling CO2 through a solution if calcium hydroxide(limewater)causes it to turn cloudy.

Question 11

What is the test for hydrogen?

Answer 11

Hold a lit splint at the end of a test tube containing hydrogen, a squeaky pop sound is made.

Question 12

How do we test for carbonates?

Answer 12

1. Add dilute acid into test tube with sample in
2. Connect test tube to a test tube with limewater in.
3. If carbonates are present, CO2 will be released from the sample and turn the limewater cloudy.

Question 13

How do we test for sulfates?

Answer 13

1.add drops of HCl, followed by drips if barium chloride solution to a test tube containing the sample.
2. If sulfate ions are present, a white precipitate if barium sulfate will form.

Question 14

How do we test for halide ions?

Answer 14

1. Add some drops of dilute nitric acid followed by silver nitrate solution to the sample.
2. Different precipitates will form depending on the halide present

Question 15

What colour precipitate does chloride give?

Answer 15

White precipitate if silver chloride

Question 16

What colour precipitate does bromide give?

Answer 16

Cream precipitate if silver bromide.

Question 17

What colour precipitate does iodide give?

Answer 17

Yellow precipitate if silver iodide.

Question 18

What colour does Li+ burn with?

Answer 18

Crimson flame

Question 19

What colour does Na+ burn?

Answer 19

Yellow flame

Question 20

What colour does K+ burn?

Answer 20

Lilac flame

Question 21

What colour does Ca2+ burn?

Answer 21

Orange-red flame.

Question 22

What colour does Cu2+ burn?

Answer 22

Green flame

Question 23

What colour is calcium hydroxide precipitate?

Answer 23

White

Question 24

What colour is a copper hydroxide precipitate?

Answer 24

Blue

Question 25

What colour is an iron2+ hydroxide precipitate?

Answer 25

Green

Question 26

What colour is an iron3+ hydroxide precipitate?

Answer 26

Brown

Question 27

What colour is an aluminium hydroxide precipitate?

Answer 27

White to colourless

Question 28

What colour is a magnesium hydroxide precipitate?

Answer 28

White

Question 29

What are the 5 tests for ions?

Answer 29

1. add dilute acid for carbonates
2. Add HCL and barium chloride for sulfates
3. Add nitric acid and silver nitrate for halides
4. Flame test
5. add sodium hydroxide to solution for metals