Chemical Analysis

Question 1

What does it mean if a substance is pure?

Answer 1

Nothing has been added to it and it is in its natural state eg (pure milk)

Question 2

What is a formulation?

Answer 2

Useful mixtures with a precise purpose that are made by following a ‘formula’

Question 3

Why are formulations important in the pharmaceutical industry?

Answer 3

• Found in cleaning products, fuels, cosmetics etc
• by altering formulation of a pill, chemists can make sure it delivers drug to correct part of body at right concentration

Question 4

How do you test for chlorine gas?

Answer 4

Chlorine bleaches damp litmus paper, turning it white. (With blue paper it May turn red for a moment because chlorine is acidic)

Question 5

How do you test for oxygen?

Answer 5

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

Question 6

How do you test for carbon dioxide?

Answer 6

Bubbling carbon dioxide through an aqueous solution of limewater, carbon dioxide causes solution to turn cloudy

Question 7

How do you test for hydrogen?

Answer 7

If you hold a burning splint at the open end of a test tube containing hydrogen, you’ll get a squeaky pop.

Question 8

What is the purpose of chromatography?

Answer 8

Used to separate the substances in a mixture. Also shows how soluble a substance is in the solvent

Question 9

What is the stationary phase in paper chromatography?

Answer 9

Chromatography paper (filter paper)

Question 10

What is the mobile phase in paper chromatography?

Answer 10

Solvent (ethanol or water)

Question 11

How do you calculate the Rf values in paper chromatography?

Answer 11

Rf= distance travelled by substance B / distance travelled by solvent A

Question 12

How to test for carbonates? (Anion)

Answer 12

Dropping a pipette to add a few drops of dilute acid containing mystery substance.
Then connect test tube to a test tube containing limewater. If carbonate ions present it will go cloudy

Question 13

How do you test for sulfates?

Answer 13

Use a pipette to add a couple of drops of dilute hydrochloric acid and barium chloride solution to a test tube containing mystery solution.
If sulfate ions are present, white precipitate will be formed (s)

Question 14

How do you test for halides?

Answer 14

Add a couple of drops of dilute nitric acid followed by a couple of tops of silver nitrate solution to mystery solution

Chloride- white ppt
Bromide-cream ppt
Iodide-yellow ppt

Question 15

What is the purpose of flame tests?

Answer 15

You can identify metal ions present in substances

Question 16

What do lithium ions produce?

Answer 16

A crimson flame (Li+)

Question 17

What do sodium ions produce?

Answer 17

A yellow flame (Na+)

Question 18

What do potassium ions produce?

Answer 18

A lilac flame (K+)

Question 19

What do calcium ions produce?

Answer 19

A orange-red flame (Ca2+)

Question 20

What do copper ions produce?

Answer 20

A green flame (Cu2+)

Question 21

What affects wavelengths emitted by an ion in flame emission spectroscopy?

Answer 21

• charge

- electron arrangement

Question 22

What are advantages of using machines?

Answer 22

• very sensitive and can detect tiny amounts of substances
• very fast and tests can be automated
• very accurate

Question 23

Why is flame emission spectroscopy more useful than flame tests?

Answer 23

They can identify different ions in mixtures and not just single metal ions

Question 24

How can flame emission spectroscopy be used to produce a line spectrum for an element?

Answer 24

• a sample is placed in a flame. As the ions heat up, their electrons become excited
• when electrons drop back to their original energy levels, they release energy as light
• the light passes through a spectroscope which can detect different wavelengths of light to produce a line spectrum