V Chemistry EOY

Hydrocarbon

Hydrocarbon

A compound of only hydrogen and carbon

Order of Alkanes (Number of Hydrocarbons before 5)

Methane, Ethane, Propane, Butane: Many Evil Pigeons Bathe

General formula for Alkanes

2n + 2; n = carbon atoms

Isomerism

Molecules that have the same molecular formula but a different displayed formula

Display Formula

(Ethane)

Structural Formula

CH3CH2CH2CH3 (Butane)

What is Crude Oil a mixture of?

Hydrocarbons

How does fractional distillation separate crude oil into fractions?

• Heat the crude oil

• Gas rises up the fractionating column

• The column is cooler at the top and hotter at the bottom

• Fractions condense when the temperature is lower than their boiling point

• Fuel oil (one shown in diagram) has a high boiling point so condenses near the bottom

Order of main fractions obtained from crude oil (top to bottom)

Refinery Gases, Gasoline, Kerosene, Diesel, Fuel Oil, Bitumen: Really Good Kids Don’t Fail Biology

Uses of: Refinery Gases

Household heating, cooking

Uses of: Gasoline

Fuel for Cars

Uses of: Kerosene

Fuel for Planes

Uses of: Diesel

Fuel for Lorries

Uses of: Fuel Oil

Fuel for Ships

Uses of: Bitumen

Road Surfacing

The Heavier Fractions: (Size, Boiling Point, Colour, Viscosity)

• Contain larger molecules meaning the intermolecular forces are stronger

• Contain substances with higher melting and boiling points

• Are darker in colour

• Are more viscous

Fuel

A substance that, when burned, releases heat energy

How does the combustion of some impurities in hydrocarbon fuel result in the formation of SO2?

• Sulfur is present as an impurity in crude oil.

• The sulfur reacts with the oxygen in the air and forms sulfur dioxide.

• S + O2 → SO2.

How does sulfur dioxide contribute to acid rain?

• Sulfur dioxide reacts with water to form sulfurous acid (H2SO3).

• This is an acidic solution as non-metal oxides are acidic

• This condenses and forms acid rain

How do oxides of nitrogen contribute to acid rain?

• Nitrogen monoxide gas can be formed in car engines and nitrogen and oxygen are both present in the air

• N2 + O2 → 2NO

• This occurs as there are much higher temperatures in a car engine so particles collide with enough energy to break the strong covalent bons in the reactants

• Nitrogen monoxide is acidic as it is a non-metal oxide

• It dissolves in water and forms acidic rain

Alkanes

Saturated (only single-bonded) hydrocarbons

Percentage of Nitrogen in air

78%

Percentage of Oxygen in air

21%

Percentage of Argon in air

0.9%

Percentage of Carbon Dioxide in air

0.04%

Combustion of Hydrogen

• Hydrogen + oxygen —> water

• 2H2(g) + O2(g) —> 2H2O(l)

• Squeaky pop is heard

Combustion of Magnesium

• Magnesium + oxygen --> magnesium oxide

• 2 Mg(s) + O₂(g) --> 2 MgO(s)

• Bright white light given off

• White solid is formed

Combustion of Sulfur

• Sulfur + oxygen --> sulfur dioxide

• S(s) + O₂(g) --> SO₂(g)

• Sulfur melts

• Burns with a blue flame

Thermal Decomposition

The breaking down of a compound (into two or more new substances) upon heating (above a certain temperature)

Formation of Carbon Dioxide from Thermal Decomposition

Metal carbonate → metal oxide + carbon dioxide

Colour of Copper Carbonate

Green

Colour of Copper Oxide

Black

Li+ (2 points)

• Flame Test

• Crimson-red flame

Na+ (2 points)

• Flame Test

• Yellow flame

K+ (2 points)

• Flame test

• Lilac flame

Ca2+ (2 points)

• Flame test

• Orange-red flame

Cu2+ (2 tests, 2 points each)

• Flame test

• Blue-green flame

OR

• Add sodium hydroxide

• Blue precipitate forms

NH4+ (3 points)

• Add sodium hydroxide

• Test with damp red litmus

• Litmus turns blue

Fe2+ (2 points)

• Add sodium hydroxide

• Green precipitate forms

Fe3+ (2 points)

• Add sodium hydroxide

• Brown precipitate forms

Cl- (3 points)

• Add nitric acid

• Add silver nitrate

• White precipitate forms

Br- (3 points)

• Add nitric acid

• Add silver nitrate

• Cream precipitate forms

I- (3 points)

• Add nitric acid

• Add silver nitrate

• Yellow precipitate forms

SO42- (3 points)

• Add hydrochloric acid

• Add barium chloride

• White precipitate forms

CO32- (3 points)

• Add hydrochloric acid

• Bubble through lime water

• Turns cloudy white

H2 (2 points)

• Test with lit splint

• Hear a ‘squeaky pop’ sound

O2¬ (2 points)

• Test with glowing splint

• Splint will relight

CO2 (2 points)

• Bubble through lime water

• Turns cloudy-white

NH3 (2 points)

• Test with damp red litmus

• Litmus turns blue

Describe the procedure involved when carrying out a flame test.

• Use nichrome whiter (made of platinum)

• Dip in hydrochloric acid

• Dip in solid/solution being tested

• Place in non-luminous (blue) flame

Why is acid added before testing for halides?

• To remove carbonate (or hydroxide) ions

Why is hydrochloric acid not used?

• Chloride ions in hydrochloric acid will cause a fake positive result

What is the name and formula of the solute in a solution of limewater?

• Calcium hydroxide

• Ca(OH)2

Formula for Mass Calculations

n = m(g) / Mr

Formula for Volume Calculations

n = v(dm³) / Vm(24dm³)

Formula for Concentration Calculations

n = c(mol/dm³) x v(dm³)

Steps for finding: Mass, Volume or Concentration

Find:

• Number

• Ratio

• Amount

Empirical Formula

Simplest whole number ratio of atoms of each element in a compound

Molecular Formula

Actual number of atoms of each element in one molecule of substance

Steps for finding: Empirical Formula

Find:

• Mass of each element

• Mr of each element

• Number of moles of each element, ratio

Steps for finding: Molecular Formula

Find:

• Empirical formula

• Mr of combined compound,

• Divide the mass by the combined Mr

• Add number found after each element

Steps for finding: x (in hydrated salt calculations)

Find:

• Number of moles of each element,

• Number of moles of water lost

• The molar ratio of: element : H2O in the form: 1 : x, first to 3sf then to the nearest whole number

Steps for finding the formula after: Combustion and Reduction

• Determine the mass of each element

• Find the empirical formula

Formula for: Hydrochloric acid

HCl

Formula for: Nitric acid

HNO3

Formula for: Sulfuric acid

H2SO4

Acid + Metal

Salt + hydrogen

Acid + Metal Hydroxide

Salt + water

Acid + Metal Oxide

Salt + water

Acid + Ammonia

Ammonium salt

Acid + Metal Carbonate

Salt + water + carbon dioxide

colour of litmus paper in acid

red

colour of litmus paper in alkali

blue

colour of phenolphthalein in acid

colourless

colour of phenolphthalein in alkali

pink

colour of methyl orange in acid

red

colour of methyl orange in alkali

yellow

SPA

Sodium, Potassium, Ammonium - All soluble

Nitrates

All soluble

Chlorides

Common chlorides are soluble. EXCEPT: Silver and Lead.

Sulfates

Common sulfates are soluble. EXCEPT: Barium, Calcium and Lead

Carbonates

Common carbonates are insoluble. EXCEPT: SPA

Hydroxides

Common hydroxides are insoluble. EXCEPT: SPA

Metal Oxides

Common metal oxides are insoluble. EXCEPT: Sodium and Potassium (SP)

Acids _____ H+ ions

Release

Bases _____ H+ ions

Accept

What can act as bases?

Metal oxides, metal hydroxides, ammonia

What are bases that are soluble in water?

Alkali

Experiment to prepare a pure, dry sample of a soluble salt from an insoluble reactant

Filtration:

• Warm the acid in a beaker (sulfuric)

• Using a spatula, add reactant into the acid and stir

• Keep adding copper oxide and stirring until no more disappears

• Filter the mixture

• Warm the filtrate to evaporate around half of the water

• Leave the solution to cool

• Filter the crystals out of this solution

• Leave the crystals in a warm place to dry

Experiment to prepare a pure, dry sample of a soluble salt from an acid and an alkali

Titration:

• Measure alkali in a glass pipette

• Add alkali to conical flask

• Add acid to burette

• Take the initial volume of acid

• Titrate until neutralisation

• Repeat until concordant results

• Repeat without indicator

• Crystalise solution

Experiment to prepare a pure, dry sample of a insoluble salt from two soluble reactants

Precipitation:

• Mix the two solutions

• Stir well and leave the mixture until a precipitate forms

• Filter the mixture using two pieces of filter paper

• Wash the precipitate using distilled water

• Transfer the precipitate to a watch glass and leave it in a warm place

rusting definition

rusting is a type of corrosion that applies specifically to iron

substances required for iron to rust

oxygen and water

chemical name for rust

hydrated iron (II) oxide

barrier method to prevent rusting

adding plastic or paint to the surface of the iron you are preventing from rusting. this prevents contact between the iron and oxygen and water.

sacrificial protection method to prevent rusting

adding small pieces of a more reactive metal such as zinc in contact with the iron that we want to prevent from rusting. zinc oxidises in preference to iron because zinc is more reactive.

galvanising method to prevent rusting

coating a piece of iron with a layer of zinc as a barrier. works the same as sacrificial protection and barrier methods but works even if scratched.

silver

Ag+

copper

Cu2+

iron(II)

Fe2+