Chemistry: Tests for Ions and Gases

Add NaOH(aq) = white ppt., soluble in excess - giving a colorless solution.
Add NH3(aq) = white ppt., insoluble in excess

Add NaOH(aq) = ammonia produced on warming

Add NaOH(aq) = white ppt., insoluble in excess
Add NH3(aq) = no ppt., or very slight white ppt.

Add NaOH(aq) = green ppt., soluble in excess
Add NH3(aq) = grey-green ppt., insoluble in excess

Add NaOH(aq) = light blue precipitate, insoluble in excess
Add NH3(aq) =light blue precipitate, soluble in excess giving dark blue solution

Add NaOH(aq) = green ppt., insoluble in excess
Add NH3(aq) = green ppt. Insoluble in excess

Add NaOH(aq) = red-brown ppt. Insoluble in excess
Add NH3(aq) = red-brown ppt. Insoluble in excess

Add NaOH(aq) = white ppt. Soluble in excess - gives a colorless solution
Add NH3(aq) = same as above

Add dilute acid - effervescence and CO2 produced

Acidify with dilute nitric acid, then add aqueous silver nitrate - white ppt.

Acidify with dilute nitric acid, then add aqueous nitrate - cream ppt.

Acidify with dilute nitric acid, then add aqueous silver nitrate - yellow ppt.

Add aqueous sodium hydroxide then aluminum foil and warm carefully - ammonia produced

Acidify and add aqueous barium nitrate - white ppt.

Add dilute HCl acid, gently warm, test for presence of sulfur dioxide - SO2 produced will turn acidified aqueous potassium manganate (VII) from purple to colorless

Turns damp red litmus paper blue

Limewater milky

Bleaches damp litmus paper

'Pops' with a lit splint

Relights a glowing splint

Turns acidified aqueous potassium manganate (VII) from purple to colorless

Red

Yellow

Lilac

Blue green

ZnS

Solubility of the salt decreases as it cools, solid crystals start to appear.

To indicate the presence of iodine

CH3COOH

Write to 1 decimal place (even if .0)

An H+ ion acceptor, pH greater than 7

Sulfur trioxide is bubbled into FUMING (concentrated) sulfuric acid

A CAREFULLY measured quantity of distilled water is added

Form acidic oxides, forms negatively charged ions, good electron acceptor = OXIDIZING agent

Fermentation - yeast + plant matter in anaerobic conditions produces carbon dioxide and ethanol, which is a fuel

Heat until a CONSTANT mass

Take 100cm3 of acid, add aqueous NaOH of the SAME concentration as the acid with a burette, monitor pH with a pH meter, HY neutralized by 100cm3 of NaOH, H2Y neutralized by 200cm3 of NaOH

Kills bacteria

Add a reactive but not too reactive metal (like aluminum) and hydrogen gas will be produced (lit splint = squeaky pop)

Don't contain neutrons

Sulphur dioxide

Transition metal elements form colored compounds

Molecules/ions that can react with acids and bases

Neutral oxide

Oxide which aren't acidic or basic - don't react with acids or bases

Alkaline

Aluminum oxide, chromium oxide, lead oxide

Crystals form because the solubility decreases as the temperature decreases.

WARM drying oven

Roast in air (heated very strongly in the blast furnace)

The brightness of the bulb will be less intense - because the difference in reactivity between copper and iron is less than between copper and zinc.

Iron

Definite volume and shape at given temp., increase slightly in size when heated - expansion, and decrease slightly in size when cooled - contraction

Fixed volume at room temp., takes shape of container, volume slightly affected by temp.

No definite shape/volume, fill volume of container, volume largely affected by temp.

All matter is made of CONSTANTLY moving particles of varying sizes, increasing temperature increases movement, heavier particles move slower than lighter ones at a given temp.

Vibrate in fixed postions, strong attraction between particles

Freedom to slide/move past each other, collide often, attraction between particles

Randomly, collide less often than liquids

Sublimation

Particles gain energy, vibrate faster, expand, forces of attraction decrease, structure breaks down

Evaporation occurs when there are particles in a liquid that move faster, so fast that if they are near the surface they have enough energy to escape and become a gas.

Particles gain energy, move faster, particles at surface evaporate, forces of attraction become negligible

The temp. at which bubbles of gas form in the liquid

A change in which the form or appearance changes, but no new substances are formed

Remains constant

A pure sample

The net movement of particles from high to low concentration down the concentration gradient.

Diffusion between a liquid and a gas

Particles move faster and collide more frequently

the constant random movement of visible particles in a fluid, as a result of continuous collisions with molecules of the surrounding medium

Increased pressure = increased boiling point

Number of protons in the nucleus of an atom

Number of nucleons (neutrons and protons) in the nucleus of an atom

Atoms of the same element, same # of protons, different # of neutrons, have simlar properties

Stable and unstable - RADIOISOTOPES

Power in nuclear reactors, medical use - treat cancer, alpha particles in smoke detectors, beta particles to find leak in pipes

18 max, however 8 gives a certain stability

They are in group 0, therefore they have a full outer shell, so they are stable and do not need to gain or lose electrons. Inert: chemically unreactive

A mixture of a metal with other elements

Ions are electrically charged particles formed when atoms lose or gain electrons.

when an atom gains or loses an electron

Oppositely charged electrons attracted and bonded by electrostatic forces

oxidation is loss, reduction is gain (of electrons)

Metallic and non metallic elements

Giant ionic lattice - regular arrangement of alternating positive and negative ions forming noble gas configuration

Electrostatic - ionic substances have a higher meltoil point than simple molecular substances

Solid at room temp., high meltoil point, conduct when molten/in solution, many (not all) are soluble in water (polar solvents), generally insoluble in non-polar solvent

Ions free to move, water molecules bond to ions - break up lattice

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

Don't conduct - no ions, volatile, generally insoluble, low meltoil point

Generally don't conduct, not volatile, generally insoluble in polar solvents, generally soluble in non-polar solvents, high meltoil point

IGCSE - an example is water (typically inorganic), extracurricular - contain bonds between atoms with very different electronegativities

IGCSE - an example is benzene (typically organic), extracurricular- contain bonds between atoms with similar electronegativities

Hundreds of thousands of atoms joined together by covalent bonds

When an element can exist in more than 1 physical form in the same state (eg. Carbon)

Conducts electricity (1 delocalized electron), formed in a hexagonal arrangement, no bonds between layers, high meltoil point

Tetrahedral arrangement, doesn't conduct (all electrons bonded), VERY hard

Glass cutter, drill bits

Similar to diamond structure (tetrahedral) 3D structure, very hard, rigid

Lattice of positive ions surrounded by a 'sea' of delocalized electrons, oppositely charged ions = strong electrostatic forces of attraction

High melting and boiling point, conducts electricity, malleable and ductile - ions cans slide over each other and the layers will hold tighter due to strong electrostatic forces of attraction between the oppositely charged ions

Anhydrous copper II sulfate (white) + water ->/<- hydrated copper II sulfate (blue)
CuSO4 . 5H2O
Anhydrous cobalt II chloride (blue) + water ->/<- hydrated cobalt II chloride (pink)
CoCl2 . 6H2O
Reaction can be reversed by addingemoving water

One or more of the reactants/products can escape

No productseactants can escape

In a closed system

Concentration of products and reactants is constant, forward and backward reactions are going at the same rate as each other

Catalysts cause reaction to reach equilibrium sooner, HOWEVER the concentration of reactants and products is the same at equilibrium with or without a catalyst

Increasing pressure = position of equilibrium moves in direction of the fewest moles of gas. Less gas is produced to try to reduce the pressure.

If temperature is increased the position of the equilibrium moves in the direction of the endothermic reaction.

Increase concentration of REACTANTS = shifts equilibrium in the direction of the forward reaction.
Increase concentration of PRODUCTS = shifts equilibrium in the direction of the backward reaction.

No new substances formed, but change to appearance of the substance.
Making mixtures, changing state, dissolving.

Process of rearrangement of the atoms in the reactants to form 1 or more products which have the same total number of each type of atom as the reactants.

Increased kinetic energy of the molecules = increased frequency of successful collisions

Reduced distance between molecules = increased frequency of successful collisions.

Increased frequency of successful collisions

Speed up chemical reactions without being changed or used up by the reaction

Amount of reactant used/time OR amount of product made/time

Small particles, large SA, can easily combust causing an explosion due to flammable surfaces.
Carbon + oxygen -> water + carbon dioxide

Increase in pressure = increase in concentration of reactants (more particles per unit volume) = increased chance of successful collisions.

Reactions initiated by light, increased light intensity = increased rate of reactionq

Silver halide salts are used in black and white photograph, silver chloride is sensitive to light and breaks down to form metallic silver which appears black. Ag+ -> Ag

Brighter the light on the film = increased rate of reaction = dark the part of the photograph appears.

Chemical process in GREEN plants, chlorophyll absorbs light energy.

oxidation is loss, reduction is gain (of electrons)

Roman Numerals, eg. Fe (II) has oxidation state 2

Potassium manganate (VII) and potassium iodide

It's an oxidizing agent and purple, it becomes colorless when reduced?

Colorless solution which..............

Provide mineral ions needed for growth in plants, minerals absorbed dissolved in water by root hair cells - when the concentration of minerals in soil becomes low farmers add fertilizers to soil.

NH4+ ammonium
NO3- nitrates

All common potassium ions dissolve in water into - K+ ions

(PO4)3-

Methane + steam -> hydrogen + carbon monoxide (to obtain hydrogen)
Hydrogen burned in air: hydrogen + oxygen -> water (removes oxygen from air to obtain nitrogen)
N2 gas + 3(H2) gas ->/<- 2NH3 gas (reversible reaction, produces ammonia, 450 C, iron catalyst, 200 atmospheres pressure)
AMMONIA IS LIQUIFIED AND REMOVED, unreacted H2 and N2 reused

Hydrogen - reacting natural gas with steam
Nitrogen - removing oxygen from air via burning air in hydrogen so water is formed

The ammonia in the salt is displaced by ammonia gas??? Check this...

78% nitrogen, 21% oxygen, 0.04% carbon dioxide, remainder - noble gases

leaded petrol, forest fires

incomplete combustion of carbon containing substances

combustion of fossil fuels containing sulfur compounds

At high temp. and high pressure in the car engine, nitrogen reacts with oxygen to form NO, which is later oxidized to NO2.
NO2 in air reacts with H2O to form nitric acid and nitrous acid.

HNO2

Passed over catalysts of palladium, rhodium, and platinum forms N2 gas and CO2

2CO + 2NO -> N2 + 2(CO2)

toxic gas, causes suffocation

irritant, acid rain

carcinogenic

major irritant, acid rain, photochemical smog

hydrated iron oxide

air and water

salt - increased concentration of ions

painting - however rust can spread under a crack
oilingreasing - prevents air and moisture reaching iron
plastic coating
plating - coating with a metal like tin or chromium
galvanising - zinc coating, continues to protect even when scratched

More reactive metal, provides source of electrons which reverse rusting reaction

Sacrificial protection is where a more reactive metal is placed in contact with the metal so that it loses electrons instead of the initial metal, eg. magnesium bar attached to ships

battery provides source of electrons

Domestic - cooking, cleaning, drinking water
Industry - coolant, solvent, cleaning, chemical reactant

colloidal clay particles, acids, bacteria, chemicals - can cause discoloration and foul taste

1 - water passed through screen
2 - aluminum sulfate added, coagulates small particles
3 - filtration through sand, specially grown microbes remove some bacteria
4 - sedimentation tank = flocculants push smaller particles together = sink to the bottom
5 - fine sand filter
6 - chlorine gas kills bacteria, sodium hydroxide neutralizes it, sulphur dioxide added if there is too much chlorine

(of a fluid, especially blood) change to a solid or semi-solid state, smaller particles clump together

a substance which promotes the clumping of particles, especially one used in treating water

cholera, typhoid

1 - large screens, filter large debris
2 - sedimentation tanks, aluminum sulfate added to coagulate so large debris sinks to the bottom
3 - remaining bacteria killed in a trickling filter by aerobic processes by microbes in gravel, BIOLOGICAL FILTRATION
4 - chlorination

Methane and carbon dioxide

CH4

1 - electromagnetic radiation from the sun passes through the Earth's atmosphere (at most wavelengths)
2 - some radiation is absorbed (warms Earth - essential for life)
3 - some radiation radiated back from Earth, absorbed by CO2 and CH4 in the atmosphere, radiation can pass through
4 - increase Earth's temp. = global warming

Extinction, melting polar ice caps = rising sea levels, increased risk of skin cancer = more UV rays hit Earth's surface

Complete combustion of carbon containing substances, respiration, reaction between an acid and a carbonate, thermal decomposition of a carbonate

Decomposition of vegetation, waste gases from digestion in animals, production and use of fossil fuels

Respiration, decomposition - decomposers respire!, complete combustion

Photosynthesis

fractional distillation

-dust removed, water vapour removed by absorbent filters
-cooled in stages to -200 C via contraction and expansion
-CO2 liquifies first and is removed
-O2 liquifies second and is removed
-N2 liquefies third and is removed
-O2 and N2 separated by fractional distillation

The FORWARD reaction is exothermic - so a cool temp shift equilibrium to make more ammonia.
However, the low temp would mean a low rate of reaction and the YIELD would be low.
Compromise temp of 450 is chosen.

High pressure will push equilibrium to produce more ammonia, however high pressure is very dangerous and expensive. Therefore a COMPROMISE pressure of 200 atmospheres is chosen.

Metals ores - eg. Copper pyrite, ZINC BLENDE (ZnS)
Volcanic regions - eg. Mount Etna, Italy
Natural gas and oil
Sulfur beds - eg. Louisiana, USA

Sulphur + air -> sulphur dioxide (combusted in air)
Dust/impurities such as UNREACTED O2 GAS removed
2(SO2) gas + O2 gas <-/-> 2(SO3) gas (reversible, 450 C, passed over catalyst on VANADIUM (V) OXIDE)
H2SO4 + SO3 -> H2S2O7 (sulfur trioxide is added to concentrated sulfuric acid to make oleum)
H2S2O7 + H2O -> 2(H2SO4) (oleum is added to CAREFULLY MEASURED amount of water to form sulfuric acid)

Forward reaction is exothermic, backward reaction is endothermic

H2S2O7

VERY violent reaction

Power stations, industry, rotting food, volcanoes

Sulfurous acid

Damage done to marble/limestone
Damage done to forests, lakes, and marine life
Acid rain
Corrosion of exposed metals

Food preservation - kills bacteria
Bleach wood pulp in the manufacture of paper

Strong DIBASIC salt
Reacts with carbonates to form normal salts, carbon dioxide, and water
Reacts with metals to form normal salts and hydrogen

Producing fertilizers - not actually in the fertilizer, removing oxidation from metals, anodizing aluminium, and car battery acid, making paints/dyes/fibres

Powerful dehydration agent, very corrosive, oxidizing agent

Making detergents, catalyst, powerful dehydrating agent

Don't add water to H2SO4 - add H2SO4 to water

Low enough to keep position of equilibrium towards the right, high enough for reasonable rate of reaction.

Not necessary for decent yield - catalyst of vanadium (5) oxide used!

H2SO3

Acidic - 5.6

flue gas contains sulfur dioxide
flue gas / sulfur dioxide is acidic
calcium carbonate reacts with sulfur dioxide
to make a salt / calcium sulfite OR neutralisation

(QUICK)LIME

SLAKED LIME

construction, lime manufacture, cement, iron extraction, glass making, NaCO3, roads

CaCO3 is used to removed sandy impurities in the iron ore (hematite), forms slag which is mostly calcium silicate

Limestone/chalk is added to clay/shale and heated to form cement. This is ground into a powder and by adding water + sand/stone chippings it is made into concrete.

Limestone is heated strongly, thermally dissociates into CaO and CO2.

mouthwash manufacture, drying agent, flue gas desulfurization, production of slaked lime, reduce soil acidity

reduce soil acidity, water purification, bleaching powder

mortar - hold bricks together

white precipitate of calcium carbonate formed

calcium bicarbonate forms when the carbon dioxide reacts with the calcium carbonate formed, calcium bicarbonate is soluble and the solution becomes clear again

Ca(HCO3)2

the breakdown of an ionic compound, molten or in aqueous solution, by the passage of electricity

Cations are positively charged ions and anions are negatively charged ions

Cathode = negative electrode, anode = positive electrode

Indicates presence of current

2Br (l) -> Br2 (g) + 2e- OXIDATION
orange-red gas

Pb2+(l) + 2e- -> Pb (l) REDUCTION
silver liquid

Hall-Héroult Process

Bauxite

Impure ore formed of Al2O3 and Fe2O3

removes Fe2O3 and sandy impurities as AMPHOTERIC Al2O3 reacts with the NaOH
IMPROVES CONDUCTIVITY

molten cryolite - reduces working temp. from 2000 C to 800-1000 C

HEP power

A3+(l) + 3e- -> Al(l)
molten Al collects on the floor of cell, syphoned out

2(O2-) -> O2- + 4e-

Graphite anodes react with oxygen gas to form carbon dioxide and must be replaced regularly!

halogens produced in preference to oxgen

hydrogen produced in preference to metals unless unreactive metals such as nickel/copper are present

anode - chlorine produced
cathode - hydrogen produced

Hoffmann voltameter

platinum - inert
graphite - cheaper, however some carbon dioxide will be produced

water ionizes poorly - sulfuric acid ionizes to provide a higher concentration of ions

4H+ + 4e- -> 2(H2)

4OH- -> 2(H2O) + O2 + 4e-

twice as much hydrogen vs oxygen produced

copper deposits, Cu2+ + 2e- -> Cu

effervescence, 4OH- -> 2(H2O) + O2 + 4e-

color fades - Cu2+ ions provide color

Cu -> Cu2+ + 2e-
Electrode becomes smaller

Cu2+ + 2e- -> Cu
Electrode becomes larger, copper deposited

Purifying copper
impure copper = anode
pure copper = cathode

anode sludge - may contain valuable heavy metals

portable!
portable source of energy

in a simple cell electricity is produced with two metal electrodes in an electrolyte like NaCl solution
What determines how well 2 metal electrodes will conduct?

Larger the difference in reactivity = better they conduct
NO

The hydrogen ions, H+(aq), are attracted to the cathode and hydrogen gas is produced.
Reduction
2H+(aq) + 2e− H2(g)

Chlorine gas is produced by the electrode process.
Oxidation
2Cl−(aq) Cl2(g) + 2e−

The sodium ions, Na+(aq), are drawn through the membrane, where they combine with the OH−(aq) to form sodium hydroxide, NaOH, solution.

Membrane cell

Hydrogen - rocket fuel, ammonia, HCl acid, hydrogen peroxide
Chlorine - disinfectants, water treatment, extraction of titanium
Sodium Hydroxide - soap, paper, aluminum extraction

Coal, oil, natural gas

Methane (CH4)

Mixture of hydrocarbons - separated into useful fractions by fractional distillation

Refinery gas - eg. Methane, bottled gas for cooking/heating, GAS
Gasoline/petrol - car fuel, liquid
Naphtha - making chemicals, liquid
Kerosene/paraffin - jet fuel and oil stoves, liquid
Diesel oil - Diesel engines, liquid
Fuel oil - fuel for ships and home heating systems, liquid
Lubricating oil - lubricants, waxes, polishes
Bitumen - surfacing roads, liquid

CnH2n+2

Meth- 1
Eth- 2
Prop- 3
But- 4
Pent- 5
Hex- 6
Hep- 7
Oct- 8
Non- 9
Dec- 10

Generally unreactive

Methane, ethane, propane, butane = gas
Pentane, hexane = liquid

A family of similar compounds with similar chemical properties due to the presence of the same functional group

The same general formula, each successive member differs by CH2

H3C

H5C2

H7C3

Not soluble in either

Commonly called natural gas, cooking and heating offices, schools, and homes.

Propane

Propane and butane

Gas lighters, portable blow lamps

Complete combustion - alkane + oxygen -> carbon dioxide + water
Incomplete combustion - alkane + oxygen -> carbon monoxide + water (+ soot which is C)

Free radical

Initiation reaction

When two radicals come together to form a stable molecule
Chlorine radical + chlorine radical -> chlorine molecule

Halogenoalkanes - solvents

Tetrachloromethane

Chloroform - anesthetic

Dry cleaning agent

Substitution reactions

Because there must be a double bond between 2 carbon atoms

Just 1 between 2 carbon atoms, additional carbon atoms bonded by single bonds

Shows which carbon atom the double bond is one
How do you indicate where a methyl/ethyl/propyl is attached? (To which carbon atom?)

Put a number in front of the formula, use 2 numbers separated by a dot
Examples - 2methylpentene, 2.4ethylheptane

Alkane molecules split up over catalyst (aluminum oxide) and heated to 500 C - forms smaller chain alkane and and an alkene

More expensive (higher temp.), better for cracking larger alkane molecules

Fuels

At 200 C an alkene is passed over a catalyst of nickel/platinum to form the corresponding alkane (eg. ethene to ethane)

At 300C, 60 atm pressure, phosphoric (v) acid catalyst, alkane reacts with steam to form corresponding alcohol (eg. Ethene to ethanol)

ADDITION reactions

There are carbon single bonds - nothing can be added
Carbon double bonds - things can be added

Alkenes - loses red brown color (reacts to join alkene double bond)
Alkanes - no color change (no double bonds)

Combine a halogen in solution with an alkene, halogen joins to halogen double bond
Ethene + bromine -> dibromoethane
C2H4 + Br2 -> C2H4Br2

Combine a halogen in solution with the substance you want to test, if the molecule is saturated there will be no color change, if the molecule is unsaturated the bromine will lose its color

Without the presence of sunlight or UV rays, but these could cause a chain reaction of substitution reactions if there is an alkane present

Joining together many similar monomers to form a large chain macromolecule called a polymer

Addition - formed from alkenes, polymer is the only product
Condensation - when monomers join, water molecules are produced

Polythene - nonbiodegradable, combusts to water and CO2 (in excess of oxygen)

Fermentation - 20-30 C, no oxygen present, anaerobic respiration of yeast
Catalytic addition of ethene to steam - 300 C, phosphoric (v) acid catalyst, 60 atmospheres pressure

Alcoholic beverage, fuel, disinfectant, solvents

Fermentation - low temp = cheap, many sources of sugar (eg. Waste sugar cane, veg waste)
Catalytic addition of ethene to steam = expensive (high temp and pressure), purer alcohol produced

CnH2n+1COOH

React with bases, produce metal salts, proton donors, poorly dissociate = weak acids - 4<pH<7, orange/yellow on universal indicator

Typical weak acid, vinegar

oxidation of alcohols

Double bond between carbon and oxygen atom

COOH, carboxyl group

An O in square brackets [O], called nascent oxygen

Oxidation of ethanol by fermentation and with acidified potassium manganate(VII) or acidified

Reaction of a carboxylic acid with an alcohol in the presence of a catalyst - esterification
Organic acid + alcohol -> ester + water