Purification And Experiments

Question 1

What is a pure substance?

Answer 1

A pure substance is a substance that is a single substance not mixed with any substance.

Question 2

What is a mixture?

Answer 2

A mixture is two substances not chemically bonded or combined together but in a mixture form.

Question 3

What is decanting?

Answer 3

It is the separation of an insoluble solid from a liquid by just pouring the liquid from the container.

Question 4

What is filtration?

Answer 4

It is the removal of a liquid From an insoluble solid.

Examples sand from water.

Question 5

What is evaporation?

Answer 5

Evaporation is used to separate dissolved solid from a solution.

Question 6

What is crystallization?

Answer 6

It is the removal of a dissolved solid from a solution forming pure crystals of the substance.

Question 7

Why are crystals formed?

Answer 7

The solubility of most solvents decrease upon cooling so as the water is cooled the solubility of the solvent decreases thus making the solute not being able to dissolve in it when it is cooled so much it becomes saturated and it can hold no more solute. Resulting in the extra solute getting out of the solvent as form of pure crystals.

Question 8

How is crystallization done without a solvent?

Answer 8

Sum solids which can be purified by melting them. As when we melt hot liquid is formed when we cool the hot liquid pure crystals form as the liquid starts to freeze this is crystallization without a phone

Question 9

What is sublimation?

Answer 9

Sublimation separate a mixture of solids one which sublimes.
Eg. Iodine is sublime in nature is so in a mixture of iodine and sand when we heat iodine it directly turns into vapour form releasing in the air when we cool it changes back to solid iodine again so it can be separated from sand upon heating and cooling easily.

Question 10

What is simple distillation?

Answer 10

Distillation separates a pure liquid from a solution.

Question 11

Why is the water inlet in the bottom of the condenser?

Answer 11

1) it is in the bottom because it can then fill the whole condenser making, the whole condenser cool as if it came from the upper side it would only fill one side of the condenser resulting in only one side becoming cool and not effective condensation taking place.
2) it also reduces thermal shock

Question 12

Why boiling chips used in distillation?

Answer 12

They are used for smooth and accurate boiling?

Question 13

Why is fractional distillation used?

Answer 13

It is used to separate two miscible or soluble liquids from one another. The liquid should have different boiling points.

Question 14

What is chromatography?

Answer 14

It is a method of separating and identifying mixtures.

Question 15

What are the various uses of chromatography?

Answer 15

1) to separate and identify mixtures of coloured substances found in foods and dyes.
2) to separate and identify substances in a drug and in blood
3) to separate and identify substances in urine to find out the athletes have been using banned drugs to enhance their performance.

Question 16

How are colourless substances identified in chromatography?

Answer 16

Locating agent is a substance that react to the substances on the paper to produce a coloured product. It is usually silver nitrate or sodium hydroxide

Question 17

How to identify an unidentified mixture in a chromatogram?

Answer 17

It is identified by its RF value
The formula for RF value=distance moved by the substance\distance moved by the solvent
REMEMBER the distance is always measured from the pencil line.

Question 18

How do you check the purity of a substance?

Answer 18

Check the purity of a substance by measuring the melting and boiling point.

Question 19

How does an impurity effect a melting point of a substance?

Answer 19

1) the greater the amount of impurity the lower the melting point.
2) the substance melts over a range of temperature.

Question 20

How do impurities effect boiling point?

Answer 20

1) Greater the amount of impurity the higher the boiling point.
2) the liquid boils over a range of temperature s

Question 21

What is the process of filtration?

Answer 21

A mixture is poured into a filter paper the insoluble substance is left Behind while the water easily passes of in the holes of the filter paper. The liquid passing through the filter is called the filtrate and the insoluble substances stuck in the filter paper is called a Residue

Question 22

What is the process of evaporation?

Answer 22

A solution is heated until water or that substance reaches its boiling point and evaporates the thing that is left can be used.

Question 23

What is solvent solute solution soluble and insoluble describe

Answer 23

1) Solvent: the liquid in which a solute dissolves the water in sea water
2) Solute : the substance that dissolves in a liquid to form a solution the salt in sea water
3) Solution: is the mixture formed when a solute has dissolved in a solvent sea water
4) Soluble describes a substance that will dissolve salt is soluble in water
5) Insoluble : describes a substance that will not dissolve sand is insoluble in water

Question 24

What is the process of crystallization?

Answer 24

The impure solid is dissolved in a solvent
The mixture of solvent and insoluble impurities is filtered to remove the impurities leaving a solution as the filtrate.
The solution is heated to evaporate the solvent until the saturated solution is formed.
God solution is allowed to cool the solid appears as professionals during cooling

Question 25

How does the process of sublimation take place?

Answer 25

Two solids are separated in such a way for example iodine which is sublime and sand are in a container iodine is heated and directly turns into vapour therefore leaving the sand behind alone when iodine is cooled it directly turns back to solid mixtures can be separated.upon heating as a sublime one laves. Then non sublime one is left Behind.

Question 26

How does simple distillation take place?

Answer 26

For example distillation of salt water is taking place a solution is put into the distillation flask and the distillation flask is heated from below thermometer is setup to note the temperature and as heat is given the temperature reaches 100 degrees boiling the water when water leaves in vapour form it is condensed in the condenser leaving pure water in the conical flask and leaving behind salt in the distillation flask.

Question 27

What is the difference between miscible and solubility?

Answer 27

. Solubility is basically a substance ability to dissolve in a solvent the more the substance is soluble the more it will dissolve a lot of solids have different solubilities. Misciblity however is a substance that is soluble and has no limit on its solubility and can dissolve in a solvent however much as you wanted to be it has no limit to its solubility. In short a miscible liquid is that that will make a homogenous substance.

Question 28

How did fractional distillation take place?

Answer 28

Two miscible liquids are placed in the distillation flask. Heat is given from below the vapour of the low boiling point substance will rise to the fractionating column. The fractionating column will allow the the pure vapours to pass by while sending back the unpure vapours. The thermometer at this time will show the temperature of the boiling point of the less boiling point substance. After the substance is in vapour form it will be condensed and sent to the conical flask. The heat will then increase and get to the boiling point of the second substances boiling point. The second substance then will boil and be condensed and then made into liquid.

Question 29

How does chromatography take place?

Answer 29

Chromatography takes place, first solution of dye is taken and a spot of it is placed on a chromatography paper. The spot should be placed on the pencil line a little above the bottom of the paper. The paper then should be put in a solvent. The solvent will move past the paper dissolving the substance or the dye taking all the dyes all substances with it.