Chemical Analysis

Question 1

What is a pure substance?

Answer 1

A single element or compound that is not mixed with any other substance

Question 2

How can you tell whether or not a substance is pure?

Answer 2

Determine its melting point. Pure substances have specific melting points

Question 3

What is a formulation?

Answer 3

A formulation is a mixture that has been designed as a useful product

Question 4

What are the steps of paper chromatography?

Answer 4

1. Draw a line near bottom of paper
2. Place small amount of substance on pencial line
3. Hang paper in beaker of solvent, making sure the solvent level is below the line
4. The paper will soak up the solvent
5. Remove the paper once the solvent is near the top. Mark the level of the solvent, known as the solvent front
6. Leave paper to dry

Question 5

What is the mobile phase of paper chromatography?

Answer 5

The solvent

Question 6

What is the stationary phase of paper chromatography

Answer 6

The paper

Question 7

What do substances with a strong attraction to the solvent do?

Answer 7

Substances with strong attractions to the solvent move quickly and travel a long way up the paper

Question 8

What do substances with a strong attraction to the paper do?

Answer 8

Substances with strong attractions to the paper move slowly and don’t travel far

Question 9

How is the Rf of a substance calculated?

Answer 9

Distance moved by substance/distance moved my solvent

Question 10

How do you identify Oxygen?

Answer 10

Insert a glowing splint into a tube of the gas

Question 11

How do you identify Hydrogen?

Answer 11

Squeaky pop test

Question 12

How do you identify Carbon dioxide?

Answer 12

Shake it or bubble it through limewater

Question 13

How do you identify Chlorine?

Answer 13

Insert litmus paper into it. It will bleach

Question 14

What are positive and negative ions called?

Answer 14

+Cations

-Anions

Question 15

List the colours of the flame tests and their corresponding metals

Answer 15

Li+ = Crimson flame
Na+ = Yellow-orange flame
K+ = Lilac flame
Ca2+ = Red-orange flame
Cu2+ = Green flame

Question 16

What are the tests for cations?

Answer 16

Flame tests

Test with sodium hydroxide solution

Question 17

What are the tests for anions?

Answer 17

Test for carbonate ions (add dilute acid, gives off carbon dioxide)
Test for sulfate ions (add dilute HCl and Barium Chloride, forms white precipitate)
Test for halide ions (add dilute nitric acid and silver nitrate)

Question 18

List the colours of the precipitates of the sodium hydroxide tests.

Answer 18

Cu2+ = Blue
Fe2+ = Green
Fe3+ = Brown
Mg2+ = White
Ca2+ = White
Al3+ = White, precipitate redissolves

Question 19

Give an example of an ionic equation of a test for sulfate ions

Answer 19

Ba2+(aq) + S04^2- (aq) –> BaS04(s)

Question 20

List the colour combinations of the test for halide ions

Answer 20

Cl- = White ppt.
Br- = Cream ppt.
I- = Yellow ppt.