Experimental chemistry

1m equals to 10dm which equals to 100 cm which equals to 1000mm

1kg is 1000 grams which is 1 000 000 mg

1t is also 1000 kilograms which is also 1 000 000 g

1kt equals to 1000 tonnes which equals to 1 000 000 kg

1 cubic metre equals to 1000dm3 which equals to 1 000 000 cm cube

We can choose the apparatus used to me sure the volume of liquids depending on the volume to be measured and also the accuracy required

Pipette- accurate fixed volumes

Volumetric flask- accurate fixed volumes but greater than 100 cm cube or 250 cm cube

Measuring cylinder- a range of volumes to the nearest 0.5

burette- a range of volumes to the nearest 0.05

When reading the volume of a liquid, we must always position our line of sight at the meniscus of the liquid, to avoid parallax error

A digital stopwatch- smallest division of apparatus is 0.01 seconds

An analogue stopwatch- smallest division of apparatus is 0.1 seconds

Water displacement- solubility in water should be insoluble to slightly soluble ( hydrogen, oxygen and carbon dioxide)

The density here does not affect gas collection ( can be insoluble or soluble)

Downward delivery- solubility in water ( can be soluble or insoluble) chlorine, hydrogen chloride and Sulfur dioxide

Density here - the density of the gas should be denser than the air so that it will go down and displace the air at the bottom

Upward delivery- the solubility can be insoluble or soluble

Density - the gas shld be less dense than the air

Methods for drying gases

Concentrated Sulfuric acid- This method is not suitable got gases which react with sulfuric acid ( ammonia) the gases that can are chlorine and hydrogen chloride

Quicklime ( calcium oxide) absorbs the moisture and carbon dioxide from the air. Therefore, it should be freshly heated before use. This method cannot be used for gases that react with calcium oxide ( carbon dioxide)

Fused calcium chloride - calcium chloride also absorbs moisture from the air, so it must be freshly heated before it can be used. this method cannot be used for substances that react with calcium chloride.

Separation techniques

Solid solid mixtures

Magnetic attraction- is used to separate magnetic solids from non magnetic solids

Example would be iron fillings from sand or sulfur powder

Sieving- is used to separate solids of different particle sizes

Suitable solvents- is used to separate a solid solid mixture where only one solute is soluble in the solvent

Solids usually have different solubilities in different solvents. An example would be sand and salt. Since salt will dissolve first in the water, the sand can be obtained through separation techniques used for solid liquid mixtures

Sublimation is used to separate a substance changes from the solid to gaseous state directly. ( common substances that undergo sublimation are iodine and naphthalene used in mothballs

Sublimation can be used to separate mixtures of substances where one sublimes on heating while the others stay stable at the sublimation temperature. the solid sublimes into a gas and moves away. When it does so, it provides a cooler surface for the gas to deposit back on and therefore changing back to the solid state which is known as the sublimate. Pure sublimate can then be easily be collected by scraping them off the surface

Filtration is used to separate insoluble solids from liquids

Evaporation to dryness is used to separate dissolved solids from it’s solvent by heating the mixture until its solvent has fully Vaporised

Crystallisation is used to obtain a pure solid from its saturated solution. A saturated solution is one in which no more solute can be dissolved

Method..

Gently heat the copper Sulfate solution in an evaporating dish to evaporate most of the liquids, until the solution is saturated. stop the heating before all the solvent has evaporated.

Cool the mixture gradually until solid copper Sulfate crystals appear within the solution

Pour the mixture through a funnel lined with filter paper to separate the solid crystals from the liquid. If more c try stake are required, they are reconcentrated and recrystallised

Crystals are washed to remove impurities or they can be dried using a few sheets of filter paper

Simple distillation is used to separate a pure solvent from its solution

The salt water is heated and boiling chips are added for smooth boiling. At 100 degree celcius, the water boils and the vapour rises and enters the condenser through the exit sidearm of the flask.

The gas comes into contact with the cooler surface of the condenser, loses heat and condenses to form liquid water. Pure water is the collected as the distillate

As more water Vaporises, the salt becomes more concentrated and therefore a residue is formed.

Miscible liquids are those that form uniform solutions ( homogenous) when mixed tgth

However oil and water are heterogenous solution when mixed together as they contain immiscible liquids

When a heterogenous solution containing two or more Immiscible liquids is left undisturbed, it separates into layers known as phases. Less dense liquid is at the top while the more dense one is at the bottom

A separating funnel is used to separate Immiscible liquids

When it separates into layers, each component can be removed by opening the tap at the bottom and collecting it in diff beakers or flasks.

Fractional distillation is when two liquids are miscible and form a homogenous solution. Therefore the separating funnel cannot be used. The difference in boiling point between two liquids would not be as large as the solid and liquid. Thus simple distillation also cannot take place.

To separate two liquids with different booking points, a fractionating column can be added to the simple distillation set up. The column contains glass beads and other small solid objects that provide a larger surface area for the vapour a to condense on

Ethanol will continue to rise and exit through the top sidearm. ( this will condense when it enters the condenser)

Water has a higher boiling point than ethanol and therefore, condenses on the cooler surface of the fractionating column into a liquid, which returns to the flask.

The length of the fractionating column determines its abilities to separate substances with boiling points that ate closer together. The ones with similar boiling point will require a longer fractionating column for better separation

Industrial applications

Oil refineries separate substances from crude oil, which is further processed Into useful chemicals like Petrol, kerosene and lubricating oil

Liquified air is separated to produce nitrogen, oxygen and argon gas for industrial applications

Ethanol produced by glucose fermentation is extracted breweries.

Sodium chloride has a higher boiling point than water

Basically table salt

Use evaporation to dryness and then use separating funnel for I’m miscible liquids

Conical flask shld not be stoppered when collecting the distillate because it would explode due to the build up of pressure in the conical flask

Methane gas can be collected via water displacement or upward delivery because it is insoluble in water and it is oso less dense than air

Molecular mass of air is 28.96 but not allowed to use dat

1m cube is 1000 dm cube which is 1000 litres

1dm cube is 1000 cm3 which is equals to 1 litre

Provide a permanent cold surface to condense the vapour effectively