Chemical analysis

Question 1

What is a pure substance in chemistry?

Answer 1

A pure substance consists of only one type of element or compound, with no impurities.

Question 2

What is the principle of chromatography?

Answer 2

It separates substances based on their different solubilities in a solvent and their attraction to the stationary phase.

Question 3

How is the Rf value calculated in chromatography?

Answer 3

distance moved by
substance
Rf = ——————————-
distance moved by
solvent

Question 4

A student performed chromatography and found an Rf value of 0.75 for one substance. If the solvent front moved 10 cm, how far did the substance travel?

Answer 4

0.75 x 10 = 7.5

Question 5

What are the tests for the following gases?
hydrogen

Answer 5

A lit splint produces a squeaky pop.

Question 6

oxygen

Answer 6

A glowing splint relights.

Question 7

carbon dioxide

Answer 7

turns into limewater milky

Question 8

chlorine

Answer 8

Bleaches damp litmus paper white.

Question 9

What is flame emission spectroscopy?

Answer 9

A technique that uses the light emitted by heated metal ions to determine their concentration and identity.

Question 10

State one advantage of using instrumental methods over chemical tests.

Answer 10

Instrumental methods are more accurate, sensitive, and faster