Topic 8Chemical Analaysis

Question 1

What is a pure substance in chemistry?

Answer 1

A substance made up of only one type of element or compound.

Question 2

How can you test for purity?

Answer 2

By checking the melting and boiling points; pure substances have specific melting/boiling points.

Question 3

What is a formulation?

Answer 3

A mixture designed as a useful product, with exact quantities of components.

Question 4

Give an example of a formulation.

Answer 4

Paint, fuels, cleaning agents, alloys.

Question 5

What is chromatography used for?

Answer 5

To separate and identify substances in a mixture.

Question 6

What does the Rf value represent in chromatography

Answer 6

The ratio of the distance moved by a substance to the distance moved by the solvent.

Question 7

How do you calculate the Rf value?

Answer 7

Rf = distance moved by substance / distance moved by solvent.

Question 8

What is the test for hydrogen gas?

Answer 8

lit splint produces a squeaky pop.

Question 9

What is the test for oxygen gas?

Answer 9

A glowing splint relights.

Question 10

What is the test for carbon dioxide?

Answer 10

Limewater turns cloudy.

Question 11

What is the test for chlorine gas?

Answer 11

Damp litmus paper turns white (is bleached).

Question 12

How can you test for metal ions using flame tests?

Answer 12

Different metals produce characteristic flame colors when burned.

Question 13

What color does lithium produce in a flame test?

Answer 13

Crimson

Question 14

What color does sodium produce in a flame test?

Answer 14

Yellow.

Question 15

What color does potassium produce in a flame test?

Answer 15

Lilac.

Question 16

What color does calcium produce in a flame test?

Answer 16

Orange-red.

Question 17

What color does copper produce in a flame test?

Answer 17

Green

Question 18

What is the precipitation test for metal ions?

Answer 18

Adding sodium hydroxide to form colored precipitates.

Question 19

What color precipitate does copper(II) produce with NaOH?

Answer 19

Blue

Question 20

What color precipitate does iron(II) produce with NaOH?

Answer 20

Green

Question 21

What color precipitate does iron(III) produce with NaOH?

Answer 21

Brown

Question 22

What is the test for carbonates?

Answer 22

Add dilute acid; carbon dioxide gas is produced if a carbonate is present.

Question 23

What is the test for sulfates?

Answer 23

Add barium chloride and hydrochloric acid; a white precipitate indicates a sulfate

Question 24

test for halides?

Answer 24

Add nitric acid and silver nitrate; different halides give different colored precipitates.

Question 25

What precipitate does chloride form with silver nitrate?

Answer 25

White

Question 26

What precipitate does bromide form with silver nitrate?

Answer 26

Cream

Question 27

What precipitate does iodide form with silver nitrate?

Answer 27

Yellow

Question 28

What is flame emission spectroscopy?

Answer 28

An instrumental method that identifies metal ions by their characteristic light emissions.

Question 29

What is the advantage of flame emission spectroscopy over flame tests?

Answer 29

It is more accurate, sensitive, and can detect multiple ions simultaneously.

Question 30

How does flame emission spectroscopy work?

Answer 30

A sample is heated in a flame, emitting light that is analyzed for its spectrum to identify metal ions.

Question 31

Why are instrumental methods like spectroscopy important?

Answer 31

They are fast, accurate, and sensitive, suitable for detecting low concentrations of substances.