Topic C1 - Experimental Techniques

Question 1

What is Paper chromatography?

Answer 1

Analytical technique for seperating and identifying mixtures of coloured compunds

Question 2

What is a suitable solvent for chromatography?

Answer 2

Ethanol or water (Te spot of sample must be above the surface of the solvent

Question 3

How does the solvent move up the paper in chromatohrapju?

Answer 3

Through capillary action

Question 4

Why won’t a spot move in chromatography?

Answer 4

A spot will not move if it is insoluble in the solvent

Question 5

Why would a substance move further in chromatography?

Answer 5

The substance/sample would have less mass and is higher in solubility

Question 6

What locating agent would you need to see a substance that has no colour?

Answer 6

ninhydrin

Question 7

What is the equation for the retention factor?

Answer 7

distance moved by the compound / distance moved by the solvent (solvent front)

Question 8

What is the filtered liquid called that is collected at the bottom?

Answer 8

Filtrate

Question 9

What is the solid separated in the funnel called?

Answer 9

Residue

Question 10

What is the condenser called in distillation?

Answer 10

Liebig condenser

Question 11

What is the column called that helps with purifying in fractional Distillation?

Answer 11

Fractionating column

Question 12

How would you seperate ethanol from water?

Answer 12

The boiling point of ethanol is 78°C whereas water is 100°C

Question 13

In food, what can purity help with?

Answer 13

Water purification ensures the safety of the drink and prevents diseases (like cholera or dysentery

Question 14

In medical productions, what can purity help with?

Answer 14

Any impurities in the durgs might cause harmful side effects and affect the drug efficacy

Question 15

What is one method of determining purity?

Answer 15

Looking at the melting point of a substance, all chemicals have a specific mpt/bpt under the specific conditions, and these are accurately known. If these points change under the same conditions, it means that theire is an impurity. For example, salt water, which ahs impurities of NaCl, has a higher boiling point than pure water.

Question 16

Why do we use pencil for the base line?

Answer 16

Because pencil does not dissolve in the solvent

Question 17

What different types of chromatography are there?

Answer 17

Paper, gas

Question 18

What is chromatography used for?

Answer 18

It is used to identify, unknown substances from known. Pure and impure substances

Question 19

What do you call the change of states from solid to liquid, liquid to gas, gas to liquid, liquid to solid, and finally solid to gas?

Answer 19

melting, boiling, condense, freeze, and sublimation

Question 20

What is changing state?

Answer 20

Having enough energy to overcome forces of attraction

Question 21

What is a pure substance?

Answer 21

Only contains one substance

Question 22

What does adding impurities/alloying do?

Answer 22

It can change the properties of the these materials (raises the boiling point, lowers the melting)

Question 23

What are alloys?

Answer 23

mixture of elements (usually metals), designed to have useful prperties for a certain purpose

Question 24

What are the differences between pure substances and mixtures?

Answer 24

pure will melt/boill at a specific temp. Whereas mixtures will melt and boil over a range of temps.

Question 25

What is decanting?

Answer 25

It is used to separate insoluble solid from liquids. It allows the solid to settle to the bottom and carefully pour off the liquid

Question 26

What is filtering?

Answer 26

More general method for speperating solids from liquids. Insoluble material stays in filter paper. Liquid collected. Useful method as both the solid and the liquid can be collected in one process. Can be sped up by using vacuum pumps and a Buchner funnel

Question 27

Describe the practical method of Crystallisation.

Answer 27

1. Add a suitable solvent (eg. water). 2. Warm the mixture in the solven and stir. 3. Filter the mixture - insoluble stuff = residue and can be dried. 4. Filtrate then evaporated and allowed to crystallise.

Question 28

Describe the practical method of distillation

Answer 28

1. Liquid is evaporated/boiled off in a round bottomed flask. 2. Gas condensed by passing it down a water cooled condenser. 3. Collect as the distillate. *Note you can also separate the liquids from a mixture of two or more liquids these are miscible (can mix), and the liquids have different voiling points

Question 29

In an experiment what is salt, water, salt and water at the beginning of the practical, and salt and water at the end of the practical.

Answer 29

Solute, Solvent, Solution, Saturated

Question 30

What is an element?

Answer 30

contains only one type of atom

Question 31

What is a mixture?

Answer 31

two/more substances that are not chemically joined. So they can be seperated and may have properties similar to what it is made of.

Question 32

What is a compound?

Answer 32

Two/more elements chemically joined in a fixed ration, so they will have different properties to the elements they ae made of

Question 33

What is a solute?

Answer 33

A substance that is dissolved in a solvent

Question 34

What is a solute

Answer 34

A substance that dissolves a solvent

Question 35

What is a solution?

Answer 35

A mixture of one/ more solutes dissolved in a solvent

Question 36

What is the boiling point

Answer 36

The temprature in which a liquid turns into a gas