Extension Science Chemistry - PowerPoint Presentation

Slide1

Extension Science Chemistry

C3 Review PowerPoint PresentationSlide2

Qualitative Analysis is where you find out what type of substance you have present.

Quantitative Analysis is when you deduce the amount of unknown sample you have.

Water samples contain IONIC COMPOUNDS which contain both CATIONS (positive) and ANIONS (negative ions).Ion tests must only give a positive result or one type of ion.

C3.1 Water TestingSlide3

Flame tests are commonly used for

CATION

(metals).Precipitate reactions can also be used by reaction the ionic solution with SODIUM HYDROXIDE as most metal hydroxides are insoluble in water.C3.1 Water TestingSlide4

Testing for the Halogens

This is performed by

acidifying the sample with dilute Nitric Acid and then reacting with Silver Nitrate to form a precipitate.This reaction works by the Halogen displacing the Nitrate in Silver Nitrate with the Halogen.Testing for Ammonium ions (NH4

+

)

Warm the solution to release the Ammonium ions as a vapour

It will turn damp red litmus paper blue.

C3.2 Safe WaterSlide5

C3.3 Ion IdentificationSlide6

Ion identification is used in many different industries. For example:

Water Industry to test for dissolved ions (both Halogens and other ions such as aluminium (linked to Alzheimer's disease).

Blood testing to test for different ions (Iron linked to Anaemia, Sodium linked to kidney function).C3.4 Safe LimitsSlide7

Types of Water

Soft water – contains low levels of ions (Na, Mg) – easily produces a lather

Hard water – contains lots of dissolved ions (Ca, Mg) – produced scum not lather – used lots of soap for cleaningPermanently hard water – cannot be easily softenedTemporarily hard water – can be softened by boiling.C3.5 Water SolutesSlide8

Calculating Concentration

Concentrations of ions are calculated generally in mgdm

-3 or gdm-3.1dm3 is equal to 1000cm3 (1 litre)To calculate concentration use the following formula:C3.5 Water SolutesSlide9

Temporarily hard water

This water is softened by boiling. It converts the Calcium Hydrogen carbonate into insoluble Calcium Carbonate (lime scale).

Softening the water improves its ability to form a lather and therefore reduce the amount of soap required.C3.6 Hard and Soft WaterSlide10

Softening Permanently hard water

This can be performed using

ION EXCHANGE. This involves Sodium ions (Na+) in the resin displacing Calcium (Ca2+) and Magnesium (Mg2+) in the water sample and softening it.

C3.6 Hard and Soft WaterSlide11

C3.7 Finding the mass of a solute in a solventSlide12

Substances can be measured in several ways. They can be:

Number of grams

Number of particlesNumber of molesOne mole of atoms is equal to the AVEGADRO number of particles (6.02X1023)The mass of one mole of atoms is equal to the Relative Atomic Mass number

(top number on periodic table)

.

C3.8 Particles and MolesSlide13

To calculate the number of moles use the following formulas:

C3.8 Particles and MolesSlide14

Making Copper Sulphate from Copper Oxide

React excess oxide (

insoluble) with accurate volume acid.Filter excess copper oxide and collect copper sulphate solution.Evaporate solvent (water) to crystallise the salt.

C3.9 Preparing Soluble SaltsSlide15

Titrations

(preparing a salt from two soluble reactants)These reactions are NEUTRALISATION REACTIONS.It involves accurately calculating the volume of ACID required to neutralise the BASE

.

An

INDICATOR

is used to deduce the point of NEUTRALISATION (end point).A pipette is used to measure the base accurately.A burette is used to add the acid accurately.

One the correct volumes have been obtained then the reaction is performed without the indicator

C3.9 Preparing Soluble SaltsSlide16

C3.9 Preparing Soluble SaltsSlide17

C3.11 Acid Alkali TitrationsSlide18

Calculate number of moles of acid used.

Write balanced equation for reaction.

Using moles of acid information, deduce number of moles of base required.Calculate concentration of base.This process also works the same in reverse.

C3.12 Titrations and CalculationSlide19

Electrolysis can only happen when

IONIC

substances are either DISSOLVED or MOLTEN.Sodium metal is produced through the electrolysis of MOLTEN Sodium Chloride.C3.13 ElectrolysisSlide20

Oxidation is the loss of electrons and happens at the

ANODE

.Reduction is the gain of electrons and happens at the CATHODE.Sodium metal is used in street lights as it gives out a yellow coloured light.

Liquid Sodium is used as a coolant in

Nuclear Reactors

as it has a high

THERMAL CONDUCTIVITY.C3.13 ElectrolysisSlide21

C3.14 Electrolysis of Sodium ChlorideSlide22

When you perform the electrolysis of a molten salt you produce ions that are discharged as atoms or molecules.

For example, when you perform the electrolysis of Lead Bromide

Pb(II)Br2 you obtain both Lead and Bromine gas.C3.15 Electrolysis of SaltsSlide23

Electrolysis of salts in solution

This involves both the electrolysis of the salt and the electrolysis of water.

The salt splits into its two component ions.The water splits into Hydrogen ions (H+) and Hydroxide Ions (OH-).To perform electrolysis you must have INERT (unreactive) electrodes as some of the products can be highly corrosive.

C3.15 Electrolysis of SaltsSlide24

Electrolysis of Sodium Chloride SolutionSlide25

C3.16 Investigating the electrolysis of Copper SulphateSlide26

Purification of Copper

An electrode of impure copper is used as the

ANODE.Pure copper is used as the CATHODE.The electrolyte is Copper Sulphate solution.C3.17 Uses of ElectrolysisSlide27

Electroplating

Electroplating is when a thin coat of valuable (or unreactive) metal is applied to a cheaper (more reactive) metal.

Silver and Gold are metals that are commonly used for electroplating.C3.17 Uses of ElectrolysisSlide28

1 mole of = 24dm

3

(at room temperature and a gas atmospheric pressure)C3.18 Molar Volume of Gases

A GAS SYRINGE is used to collect gases during reactions to allow molar gas calculations to be performedSlide29
Slide30

Nitrogenous fertilisers (ones that contain Nitrogen) are manufactured from

AMMONIA

. These fertilisers are used to promote plant growth. These fertilisers increase the yield of crops that are produced.If these fertilisers are used excessively then this can lead to run off into rivers and lakes (or any other water source). This results in excessive plant growth (EUTROPHICATION). When these plants die they decompose by bacteria which uses up the OXYGEN.

C3.19 Fertilisers and the Haber ProcessSlide31

The

HABER

process is a REVERSIBLE reaction which will reach DYNAMIC EQUILLIBRIUM.Dynamic equilibrium is where the FORWARDS and BACKWARDS reactions are happening at the

same rate

.

C3.19

Fertilisers and the Haber ProcessSlide32

When

AMMONIA

is formed it releases heat (EXOTHERMIC). This is the FORWARDS reaction.The reverse reaction will be the opposite which makes it ENDOTHERMIC (takes in heat)When DYNAMIC EQUILLIBRIUM

is reached these two reactions occur at the

SAME RATE

.

Adjusting the temperature and pressure will affect the position of the equilibrium, favour the PRODUCT or REACTANT.

C3.20 The Haber processSlide33

N

2

+ 3 H2 ⇌ 2 NH3Reactant = 4 moleculesProducts = 2 moleculesPressure and the Haber processIf you increased the pressure of the reaction the equilibrium would favour the

PRODUCTS (move to the right)

. This is because the particles are being forced closer together and therefore more likely to react.

Temperature and the Haber process

As the reaction is EXOTHERMIC it favours cooler conditions (it releases energy into the surrounding environment).

An increase in temperature would move the equilibrium to the

left (favour the reactants)

.

A low temperature would increase the yield but slow the rate of reaction.

C3.20 The Haber processSlide34

Optimal conditions are used to ensure that the maximum possible yield is produced safely and at a sufficient rate to be economically viable.

Temperature – approx. 450OC

Pressure – 200atm (200 times atmospheric)Catalyst – Iron catalystA catalyst increases the rate of reaction without ever being used in the reaction. It works by lowering the activation energy for the reaction (energy required for a successful collision)If the temperature or pressure is too high then there can be safety implications and too low will result in a lower yield.

C3.20 The Haber processSlide35

Ethanol (alcohol) can be produced by the fermentation of

CARBOHYDRATES

(sugars).Fermentation occurs when YEAST convert sugars into alcohol. The yeast act as an ENZYME.For this to happen successfully the following conditions must be sustained:Kept warm (allow the bacteria to work successfully, too hot will kill them)Anaerobic conditions (no oxygen)

C3.21 FermentationSlide36

Different types of alcoholic drink contain different percentages of ethanol. The higher the alcohol content the higher % it is given.

1 unit of alcohol = 10cm3 pure ethanol

The effects of alcohol are:Slower reaction timesViolent/aggressive behaviourLoss of balance/coordinationVomiting and faintingDehydrationProlonged alcohol consumption can result in an increased risk of HEART DISEASE, STROKE or

LIVER CIRROHISIS

.

Alcoholic spirits are made by

FRACTINAL DISTILLATION where the ethanol is removed first and the water is left behind (increasing the alcoholic content)C3.22 Alcoholic DrinksSlide37

Ethanol can be produced in two main ways:

1. Fermentation

– sugars are turned into ethanol and carbon dioxide through the anaerobic respiration of YEAST. 2. Hydration of Ethene (crude oil fraction) – reacting ethene with steam in the presence of a catalyst (addition reaction)

C3.23 Ethanol productionSlide38

Each method of Ethanol production has both social, environmental and economical advantages and disadvantages.

This information needs to be evaluated to determine the best method of production for individual cases.

Making EtheneEthene can be made by the cracking of CRUDE OIL but also the DEHYDRATION of Ethanol.C3.23 Ethanol productionSlide39

Alkanes

– a hydrocarbon containing only

C-C bonds.Alkenes – a hydrocarbon containing at least one C=C bond.Alcohol – a hydrocarbon containing at least one

–O-H group

.

C3.24 Homologous series

A HOMOLOGOUS series is a series of compounds that have the same general formula and similar chemical properties but have variation in boiling points.Slide40

C3.24 Homologous seriesSlide41

Ethanoic

acid is a

CARBOXYLIC ACID.It is the active ingredient in VINEGAR.It is produced by the OXIDATION of ethanol (under aerobic conditions).It has a sharp, sour taste and can be used as a PRESERVATIVE.

Ethanoic

acid reacts with metals to form salts (ending –

ethanoate

).Carboxylic acids react in the same way as normal acids. They are classified as weak acids.Carboxylic acids are named in the same way as other homologous series. Their ending is –

anoic

acid

.

Their functional group is

–COOH

.

C3.25

Ethanoic

acidSlide42

Esters are made during the reaction of

ALCOHOLS

and CARBOXYLIC ACIDS.They are commonly used as FLAVOURINGS and FRAGRANCES as they have distinctive smells and tastes.Ethanol reacts with

ethanoic

acid

to from the ester

ETHYL ETHANOATE.

Esters can also be turned into

FIBRES

to make

FABRICS – POLYESTER

.

Polyesters can be recycled to form

FLEECE

.

C3.26 EstersSlide43

Fats and Oils are big esters. The only difference is fats are

SOLID

at room temperature where as oils are LIQUID.Soaps can be made from fats and oils by heating with a concentrated alkali.Oils are commonly UNSATURATED (contain C=C bonds).

Fats are

SATURATED

(contain C-C bonds).

To turn an oil into a fat you must HYDROGENATE it (addition of Hydrogen)C3.27 Fats, Oils and SoapsSlide44

How do Soaps work?

A soap can be shown as a tadpole shape – head is water loving (HYROPHILLIC) and tail is water hating (HYDROPHOBIC).

The head has a negatively charged oxygen ion (anion).The tail is a hydrocarbon (water hating)Hydrophobic tail sticks into grease.Hydrophilic end sticks out to attract water.Grease particle surrounded by hydrophilic heads.Removed by water attraction (grease can now mix with water) C3.27 Fats, Oils and Soaps