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Chemistry

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Chemistry

Principles of Chemistry

Atom structure and definition

smallest and simplest particle found in the periodic table of elements

⁠

Definition: Isotope and Calculating Isotopic Abundances

- two atoms with the same proton number, hence the same element, however with a different number of neutrons, hence a different mass number

(% abundance x mass number) + (% abundance x mass number) / 100

Eg. Calculate the isotopic abundance of Chlorine-37 of 25% abundance and Chlorine-35 of 75%

(37 x 27) x (35 x 75) / 100 » 35.5

Arrangement of the Periodic Table

order of ascending proton number (atomic number)

GROUPS:

vertical, is the number of electrons in the valence shell (outer electrons)

PERIODS:

horizontal, is the number of shells

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Metals and Non-Metals: Characteristics, position in the periodic table

METALS:

shiny

sonorous

brittle

malleable

hard

good conductors

NON METALS

dull

soft

bad conductors

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Understand why noble gases don’t react, while others do

Atoms react to have a full outer shell

Noble gasses already have a full outer shell, so they don’t tend to react.

They are group 0

IONIC BONDING

Formation of Ions

gain or loss of electrons

when the number of electrons is not equal to the number of protons, thus the atom has an overall charge

note: know the ions of hydroxide (Oh-!) ammonium (NH4+), Carbonate (CO3-2), nitrate (No3-), Sulfate (SO4-2)

Formation and Properties of Ionic Bonds

between a metal and a non metal

exchange of electrons to have a full outer shell

elements become ions, thus having an overall opposite charge, which causes and electrostatic attraction

Properties:

Very High melting & boiling points

the electrostatic attraction between the ionic bonds are very hard to break and require a lot of energy

giant ionic lattices also have very high melting points

Do not conduct electricity unless aqueous

there are no free electrons in ionic bonds unless aqueous

note: draw a dot and cross diagram

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COVALENT BONDING

Formation and Properties of Covalent Bonds

between two non metals

rely on INTERMOLECULAR FORCES

sharing of electrons to obtain a full outer shell

all diatomic molecules are covalently bonded

Properties:

do not generally conduct electricity, they don’t have free electrons

an increase of relative atomic mass of a covalently bonded molecule results in an increase in boiling and melting point. there are more intermolecular forces to break

giant covalent lattices have a high melting and boiling point

simple covalent molecules have low melting and boiling point, as they rely on intermolecular forces which are easy to break.

Structures and Properties of Graphite, B-fullerine and Diamond

all are ALLOTROPES of carbon »» different arrangements of the same element (Carbon)

GRAPHITE

HEXAGONAL arrangement of carbon in layers held together by intermolecular forces, which slide easily. thus, usually used for lube. simple carbon, so low melting point

B-FULLERENE

hexagonal arrangement in a circle, each carbon atom is bonded with 3 other

CARBON

each carbon is bonded with 4 other, creating a giant covalent lattice

thus, very hard, not conductor and high melting point. (no free electrons)

METALLIC BONDING

Formation and properties

Between two metals

attraction of metal atoms in a sea of delocalized electrons

PROPERTIES

» due to the delocalized electrons, metallically bonded molecules are very good at conducting electricity and heat (heat travels through electrons)

» the sea of electrons allows nuclei to shift, so it is malleable

Inorganic Chemistry

Group 1: Alkili Metals. trends, properties and explanation of their properties

Trends:

- moving down the group, the reactivity increases

- reaction with water to form METAL HYDROXIDE + HYDROGEN

- reaction with oxygen to form METAL MONOXIDE

all alkili metals have one outer electron

their reactivity is measured using reactions with water and air

as you move down the group,

here are more shells, thus more distance between the outer electron and the nucleus.

there are also more electrons shielding

As the nucleus positive charge attracts the electron, the increase of distance makes the attraction weaker, thus easier to react and lose the electron

Group 7: Halogens. Trends, properties and explanation of their properties

Trends:

- moving down the group, reactivity decreases.

- moving down the group, melting and boiling points increase

all halogens have 7 outer electrons: they only need 1 to complete their shell.

their reactivity is measured using displacement reactions

here are more shells, thus more distance between the outer electron and the nucleus.

there are also more electrons shielding

As the nucleus positive charge attracts the electron, the increase of distance makes the attraction weaker, thus harder to attract another electron

Group 7: colours and states of the halides

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Gases in the Atmosphere

Approximate percentages of gases in the air

78% nitrogen

21% oxygen

0.04 % co2

0.9% argon

How to determine percentage by volume of oxygen ( 2 experiments )

1. iron fillings on a seringe

reaction will occur to absorb the oxygen

Measure initial and final volume

subtract

2. place a bell jar on a large container of water.

pleace phosphorus inside the bell jar.

it will ignite and absorb the oxygen

final - initial = oxygen volume

Reactions

Describe the Combustion of magnesium, hydrogen and sulfur

Magnesium:

- white bright flame

- white powder is produced (magnesium oxide)

Hydrogen:

- Exothermic

- produces water

Sulfur:

- colourless, poisonous gas is formed

Thermal Decomposition of Metal Carbonates

breaks into METAL OXIDE AND CARBON DIOXIDE

Rust vs Corrosion and prevention

Corrosion: oxidation of metals

Rust: the reaction of iron in the presence of oxygen and water

Prevention: galvanizing, sacrificial protection, paint / oil / plastic coating

REDOX REACTIONS

takes place in all displacement reactions

oxidation is loss of electrons

reduction is the gain of electrons

oxidizing agent: element that takes electrons from another and is reduced

reducing agent: element that looses electrons and is oxidized

Reactions: ACID + METAL; ACID + BASE; ACID + METAL CARBONATE

Acid + metal » salt + hydrogen

Acid + base » salt + water

Acid + metal Carbonate » salt + water + carbon dioxide

Extraction

describe two methods of extraction

Displacement reactions

reaction with a more reactive element that displaces a bond

is effective for most element

Electrolysis

uses a flow of electrical current through a molten liquid to extract an element on its pure form

is effective for the most reactive elements in the reactivity series

the current flows in two metal bars: an ANODE and a CATHODE

Electrons flow towards the cathode

Hence, the anode is more positive and the cathode. Thus, it attracts the negatively charged ions, called anions

the negatively charged cathode attracts the positively charged ions, called cations

Anode » anions

cathode » cations

⁠

the lead bromide must be aqueous, as it is the only way that ionically bonded compounds can conduct electricity

anions are negative because they have more electrons than normal.

the anode takes away those extra electrons to leave the original element

cation are positively charged because they lack electrons

the cathode gives them the lacking electrons to leave the original element

Define: Ores and Alloys

Ores is a metal made of several elements found in the earths crust due to its reactivity

Alloys is a mixture of two or more elements.

only pure elements have a fixed and exact boiling point, so alloys dont. they are also stronger due to their atomic structure.

Properties and uses of Aluminium, Copper, iron low-carbon steel, high carbon steel and stainless steel.

Aluminium: used for food cans

Copper: good conductivity, wires

iron: car bodies,

low carbon steel: car bodies

high carbon steel: cutting -

stainless steel: sinks

Acids, Alkilis and Bases

Colours of Litmus, methyl orange, phenolphthalein and universal indicator

Litmus

Acidic: red

Neutral: stays its original colour

Alkaline: blue

Phenolphthalein

Acidic: colourless

neutral: colourless

alkaline: P!nk

Methyl Orange:

Acidic: red

Neutral: Orange

Alkaline: Yellow

Universal Indicator:

Acidic: red

Neutral: green

alkaline: purple

Define Alkilis and Acids in terms of protons. Define Neutralization Reactions

ACID :

proton donors (H+)

are acidic when aqueous

eg. HCL » H + CL

ALKALIS

give our hydroxide ions (oh- )

are alkiline when aqueous

are called bases when solid

eg. NaOH » OH + Na

Neutralization reactions are a reaction between an alkali and an acid that produces a SALT AND A WATER

the H+ from the acid combines with the OH- from the base to form water H2O

Which three compounds can act as bases?

Metal Oxides,

Hydroxides,

Ammonium

Titration (triple only)

A reaction to find out the exact volume of alkali needed to neutralize a certain volume of acid

Solubility

Solubility rules for: Nitrates, Chlorides, Sulfates, Carbonates, Hydroxides and (Sodium, potassium and ammonium )

sodium, potassium and ammonium are soluble

all nitrates are soluble

all chlorides are soluble EXCEPT LEAD AND SILVER

all sulfates are soluble EXCEPT LEAD; BARIUM AND CALCIUM

are carbonates are INsoluble EXCEPT sodium potassium and ammonium

all hydroxides are INsoluble EXCEPT sodium, potassium and calcium

describing exeriments yeah no

Chemical Tests

describe the tests for common gases: hydrogen, oxygen, carbon dioxide, ammonium, chlorine

Hydrogen

lighted splint on test tube filled with hydrogen, it will give a “SQUEAKY POP”

oxygen

glowing splint on a test tube filled with oxygen, it will re ignite

Carbon Dioxide

test tube filled with carbon dioxide and lime water. it will turn clowdy

Ammonium

test tube filled with ammonium. Put a red litmus paper. it will turn blue

Chlorine

test tube filled with chlorine. Put a blue litmus paper. it will turn white:

Describe the flame tests for the following metals: lithium, sodium, potassium, calcium, copper

Lithium: red

sodium: yellow

potassium: lilac

calcium: orange

copper: green

Describe the tests for the following cations: ammonium, copper, iron 2, iron 3 using SODIUM HYDROXIDE

add red litmus paper, it turns blue

Copper turns blue

iron turns green

iron 3 turns brown

Describe the tests for the following anions: Chlorine, Bromine and Iodine. Sulfate Ions and Carbonate

USE NITRIC ACID AND SILVER NITRATE FOR CHLORINE; BROMINE AND IODIDE

chlorine turns white

bromine turns cream

iodide turns yellow

SULPHATE USING BARIUM CHLORIDE

sulfate turns white

CArbonates use Hydrochloric acid turns milky

Organic Chemistry

Define an Alkane, Alkane, Alcohol, carboxylic acid , ethene and

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