Chemical Analysis

Question 1

What is a pure substance?

Answer 1

A single element or compound, not mixed with any other substance

Question 2

What are the properties of pure substances?

Answer 2

melts and boils at specific temperatures

Melting point and boiling point data used to distinguish from mixtures

Question 3

What is chromatography’s purpose?

Answer 3

Used to separate mixtures
Provides information for substance identification

Question 4

What are the 2 components of chromatography?

Answer 4

Stationary Phase
Mobile Phase

Question 5

What is the equation for the rf value?

Answer 5

Rf = distance moved by substance/distance moved by solvent

Question 6

What is the significance of the Rf value?

Answer 6

• Different compounds have different Rf values in different solvents.
• Used to help identify compounds

Question 7

What will compounds in a mixture do in chromatography compare dto a pure substance?

Answer 7

• Compounds in a mixture may separate into different spots depending on the solvent.
• A pure compound produces a single spot in all solvents.

Question 8

What is the test for hydrogen?

Answer 8

• Hold a burning splint at the open end of a test tube containing hydrogen
• Hydrogen burns rapidly with a pop sound

Question 9

What is the test for oxygen?

Answer 9

• Insert a glowing splint into a test tube of oxygen
• The splint relights in oxygen

Question 10

What is the test for carbon dioxide?

Answer 10

• Shake or bubble carbon dioxide through an aqueous solution of calcium hydroxide (lime water)
• Limewater turns milky (cloudy) in the presence of carbon dioxide

Question 11

What is the test for chlorine?

Answer 11

• Damp litmus paper is put into chlorine gas
• Litmus paper is bleached and turns white in the presence of chlorine