C-8 Chemical Analysis

Question 1

What is a pure substance

Answer 1

• A pure substance is a single element or compound not mixed with any other substance

Question 2

What is a quality of a pure substance

Answer 2

• Melt and boil at specific temperatures

Question 3

What can be used to determine pure substance

Answer 3

• Melting point
• Compare to mixtures
  _ closer to boiling point the more pure

Question 4

What effect do impurities have on mixtures qualities

Answer 4

• Effect meting and boiling point
• Low melting point and increased melting range
• Increased boiling point- increased boiling range

Question 5

• What is purity in everyday language

Answer 5

• A pure substance is one without anything added to it

E.g Pure Milk

Question 6

What is a formulation

Answer 6

• A formulation is a mixture that has been designed with a useful product

Question 7

What are the products of formulations

Answer 7

Complex mixtures in which each chemical has a specific purpose

Question 8

How are formulations made

Answer 8

• Mixing compounds carefully messed carefully to ensure properties of product-
• e.g medicine and its shell life and its curing properties

Question 9

What are some example of formations

Answer 9

• Fuels
• Cleaning agents
• Medecine
• Paints
• Alloys
• Food
• Fertiliser

Question 10

How are compounds identified

Answer 10

• Will have ratios or percentages of each product which gives indication

Question 11

What can chromatography be used for

Answer 11

• Used to separate mixtures and give help identifying substances

Question 12

• What does chromatography involve

Answer 12

• Stationary and mobile phase

Question 13

What is a stationary phase

Answer 13

• Where molecules can’t move- solid or thick liquid

Question 14

What is a mobile phase

Answer 14

• Where molecules can move- liquid or gas

Question 15

What does separation depend on

Answer 15

• Distribution of substances between phases- whether it spend more tim win stationary or mobile phase

Question 16

What is the calculation for the Rf value

Answer 16

• Distance moved by substance // Distance moved by solvent

Question 17

How does chromatography work

Answer 17

• Constantly move between mobile and stationary phase
• Mobile phase moves through stationary phase- anything dissolved in mobile phase moves through it
• Chemicals that spend more time in mobile phase move further
• As they spend different amounts of time in mobile phase they move and end at different points

Question 18

What happens to pure substances in chromatography

Answer 18

• Pure substances won’t separate

Question 19

• What does the amount of time spent in the mobile phase depend on

Answer 19

• Solubility- more time in mobile phase move further-

- How attracted to paper- wills pend more time in mobile phase

Question 20

How can you test for pure substances in a mixture

Answer 20

• Get mixture and known pure substances and run chromatography
• Compare distances of spots and if two Rf values match up- pure substance may be present
• Test in other solvent to make sure

Question 21

• What is the test for chlorine

Answer 21

• Chlorine bleaches damp litmus paper white

Question 22

• What is the test for oxygen

Answer 22

• Put glowing split into test tube of oxygen- if relights- oxygen is present

Question 23

• What is the test for carbon dioxide

Answer 23

• Bubbling or shaking through calcium hydroxide- limewater- it will go cloudy

Question 24

What is the test for hydrogen

Answer 24

• Lit splint at end of test tube- squeaky pop