Chemical Analysis

Question 1

Positive flame test for lithium

Answer 1

Crimson flame

Question 2

Positive flame test for sodium

Answer 2

Yellow flame

Question 3

Positive flame test for Potassium

Answer 3

Lilac flame

Question 4

Positive flame test for calcium

Answer 4

Orange-red flame

Question 5

Positive flame test for copper

Answer 5

Green flame

Question 6

Sodium hydroxide precipitate reaction: positive test for copper (III)

Answer 6

Blue precipitate forms.

Question 7

Sodium hydroxide precipitate reaction: positive test for iron (II)

Answer 7

Dark green/blue precipitate forms.

Question 8

Sodium hydroxide precipitate reaction: positive test for iron (III)

Answer 8

Brown precipitate forms.

Question 9

Sodium hydroxide precipitate reaction: positive test for magnesium

Answer 9

White precipitate forms, does not dissolve when excess NaOH is added

Question 10

Sodium hydroxide precipitate reaction: positive test for calcium

Answer 10

White precipitate forms, does not disolve when excess NaOH is added.

Question 11

Sodium hydroxide precipitate reaction: positive test for aluminium

Answer 11

White precipitate forms, dissolves when excess NaOH is added.

Question 12

What is the test for halides?

Answer 12

• Add a few drops of dilute nitric acid
• Add a few drops of silver nitrate solution

Question 13

Positive test for chloride ions?

Answer 13

A white precipitate forms.

Question 14

Positive test for bromide ions?

Answer 14

A cream precipitate forms.

Question 15

Positive test for iodide ions?

Answer 15

A yellow precipitate forms.

Question 16

What is the test for carbonates?

Answer 16

• Add a few drops of dilute acid
• Test for carbon dioxide being produced.

Question 17

What is the test for sulfates?

Answer 17

• Add a few drops of dilute HCl
• Add a few drops of barium chloride solution

Question 18

What is the positive result for the sulfates test

Answer 18

A white precipitate forming.

Question 19

What is the test for chlorine gas?

Answer 19

Blue litmus paper
Bleaches

Question 20

How does chromatography separate substances?

Answer 20

By solubility and affinity for the paper.

Question 21

What is the stationary phase?

Answer 21

The chromatography paper.

Question 22

What is the mobile phase?

Answer 22

The solvent

Question 23

How do you calculate the RF value?

Answer 23

Distance moved by substance / Distance moved by solvent

Question 24

How does flame emission spectroscopy work?

Answer 24

• Sample is put into a flame (electrons are exited)
• Energy is given out as electrons drop back to lower energy levels
• This is passed through a spectroscope
• An emission spectrum is produced

Question 25

What is flame emission spectroscopy used to identify?

Answer 25

Metal ions and compounds.

Question 26

How does the melting point of impure substances differ to pure substances?

Answer 26

Impure substances melt over a range of temperatures (the more impure it is the larger the range).