C1: experimental chemistry

Question 1

1m^3 = ? dm^3

Answer 1

1000dm^3

Question 2

describe pipette, volumetric flask, measuring cylinder, burette

Answer 2

pipette -> multiples of fives, 25.0 cm^3 or 10.0cm^3. fixed volumes of substances only, accurate

volumetric flask ->measures accurate fixed volumes that are larger,
e.g. 100 cm3 or 250 cm3

measuring cylinder -> whole numbers only, not accurate, measures nearest to 0.5 cm^3 eg, 31.5 cm^3 or 23.0 cm^3

burette -> measures a range of volumes to the nearest 0.05 cm^3,
e.g. 31.55 cm^3 or 23.00 cm^3

Question 3

how should you read the burette

Answer 3

• ## eyes shld be perpendicular to reading

Question 4

state the methods for collecting gases and describe

Answer 4

1. water displacement, gas shld be insoluble, density doesn’t matter. common gases collected by this method is hydrogen oxygen carbon dioxide.
   **don’t use water displacement to collect a dry gas as it’ll wet it again
2. downward delivery, gas is denser than air. common gases that collect this is chlorine, hydrogen chloride, sulfur dioxide
3. upward delivery, for when gas is less dense than air. common gases are ammonia

Question 5

state the methods for drying gases and describe

Answer 5

1. concentrated sulfuric acid
   acidic gases, eg chlorine, carbon dioxide, hydrogen chloride, sulfur dioxide
   X ammonia bc it’s alkaline and will react ( neutralisation) w the acid
2. quicklime(calcium oxide)
   alkaline gases, eg ammonia
3. fused calcium chloride
   neutral gases, eg hydrogen and oxygen

*calcium oxide absorbs moisture and carbon dioxide from air, it must be heated before use

Question 6

separation techniques for solid solid

Answer 6

magnetic, sieving, sublimation, using suitable solvents

Question 7

what is solvent and solute

Answer 7

solvent, liquid that dissolves solids
solute, solid that dissolves in the solvent

A solute dissolves in a solvent.

Question 8

separation techniques for solid liquid mixtures

Answer 8

filtration, evaporation to dryness,crystallisation, simple distillation

Question 9

immiscible vs miscible

Answer 9

miscible, describes a homogeneous mixture, forms a uniform solution

immiscible, heterogeneous mixture, forms a nonuniform solution, separyes into layers known as phases. eg oil and wayer

Question 10

separation techniques for liquid liquid mixtures

Answer 10

• separating funnel, for immiscible solutions
• fractional distillation, for miscible solutions
• simple distillation, miscible solutions

chromatography
**if solution is insoluble, the dot will not move from start line
start line is pencil

Question 11

chromatography, how to measure the solubility of solvent

Answer 11

Rf value = distance travelled by the substance(solvent front)/distance travelled by solvent

Question 12

how do you draw the methods of collecting gases and drying gases?

Answer 12

cannot insert pic refer to gc

Question 13

what is sublimation

Answer 13

when one substance changes from solid to gas directly
it separates solids when one solid is able to sublime

Question 14

what is filtration

Answer 14

separates insoluble solid from liquid

Question 15

filtrate vs residue

Answer 15

filtrate is the liquid that passes through the filter
residue is the solid that remains on the filter

Question 16

what is evaporation to dryness

Answer 16

• Separates a dissolved solid from its solvent
• The mixture is heated until all the solvent has vaporised

Question 17

what is crystallisation

Answer 17

• Separates a pure solid from its saturated solution
• A saturated solution is one in which no more solute can be dissolved.

Question 18

explain crystallisation rq

Answer 18

1. heat the solution till saturation point ( dip a glass rod to test)
2. cool the solution till crystals appear
3. our mixture through a funnel with filter paper to collect crystals
4. wash crystals with cold distilled water and dry between filter paper

saturation: when theres too much crystals compared to water for crystal to dissolve

Question 19

explain simple distillation

Answer 19

it separates a pure liquid/solvent from its solution

Question 20

what is distillate

Answer 20

the water collected in the flask after simple distillation

Question 21

how should the water be flowing in the condenser

Answer 21

in the opposite direction to the distillation

Question 22

what is a mixture

Answer 22

• two or more substances that are not chemically combined

Question 23

what is separating funnel

Answer 23

it separates immiscible liquids
* denser liquids sink ( at the bottom where the tap is)

Question 24

what is chromatography

Answer 24

separates a mixture of substances which have diff solubilities in a solvent

Question 25

how do you conduct chromatography with colourless substances

Answer 25

using locating agents, they are chemicals that react with the colourless substances to form coloured spots, if there’s nothing its insoluble in the locating agents and you shld change solvent

Question 26

what is fractional distillation and explain it’s process

Answer 26

it separates miscible liquids with different boiling points
eg, separating ethanol and water
As the solution is heated up, Ethanol and water vapour evaporates and rise up ( evaporation happens at any temperature)
Fractional distillation has a column called the fractionating column with glass beads in it, allowing a large surface area for vapour to condense resulting in better separation. Since water has a higher boiling point than ethanol the water vapour condenses on the cool surfaces within the fractionating column and returns to the flask while the ethanol continues to rise.
then same process as simple distillation

Question 27

pure vs mixture

Answer 27

pure
* specific melting or boiling point under fixed conditions
mixtures
* melt or boil over a range of temperatures