Chemistry 101

CHEMISTRY 101   Notes for Pure Chemistry so you won’t die for O’ levels     All information accurate as of 2020   All credits to Qin Guan for his notes (and me for making the docs)     TABLE OF CONTENTS     INSTRUCTIONS FOR USE     EXPERIMENTAL TECHNIQUES AND MEASUREMENTS   PURIFICATION AND SEPARATION   KINETIC PARTICLE THEORY   ELEMENTS, COMPOUNDS, AND MIXTURES   ATOMIC STRUCTURE   IONIC BONDING   COVALENT AND METALLIC BONDING   CHEMICAL EQUATIONS   STOICHIOMETRY AND THE MOLE CONCEPT   ACIDS AND BASES   SALTS   QUALITATIVE ANALYSIS   SPEED OF REACTION   ENERGY FROM CHEMICALS   AMMONIA   AIR AND THE ENVIRONMENT   REDOX   METALS   THE PERIODIC TABLE   ELECTROLYSIS     1

INSTRUCTIONS FOR USE   Hello people! Welcome to Chemistry 101!       Feel free to ​ print, download, or make a copy ​ of these notes! Here is the link to the   original ​ Google Docs ​ :   https://docs.google.com/document/d/1ODpZq-XEX3ZVCgag6TEU-2IOEGtURe9odrX6c9w4zz U/edit?usp=sharing     This set of notes was made in 2020, do note the following topics that ​ have not ​ been   included in this set of notes:   FUELS AND CRUDE OIL   ALKANES AND ALKENES   ALCOHOLS, CARBOXYLIC ACIDS AND ESTERS   MACROMOLECULES     Hopefully people will benefit from this and do well for chemistry. This set of notes will   help you to break everything down into smaller concepts so that it’s easier for digestion   and understanding. :)     Hopefully less people will die for O’ levels Chemistry (Pure) after using this set of notes.     I would like to fully credit myself for making the google docs and doing notes for all the   S4 chapters. I would also like to credit my friend Qin Guan, for writing all notes for all   the S3 chapters and allowing me to convert it into a google docs.       Jun Ci   (The human who did the google docs)     2

EXPERIMENTAL TECHNIQUES AND   MEASUREMENTS   PHYSICAL QUANTITIES     Physical   Quantity   Unit   Conversion   Measurement   Mass   Kg   1kg = 1000g   Beam balance, Electronic   balance   Volume   cm ​ 3   1cm ​ 3 ​ = 0.001 liters   Measuring cylinder,   Burette     dm ​ 3   1dm ​ 3 ​ = 1000cm ​ 3 ​ = 1 liter     Time   Seconds (s)   1h = 60min= 3600s   Stopwatch     Minutes   (min)         Hours (h)       Temperature   Celsius (ºC)   -   Thermometer     Kelvin (K)   Celsius + 273K     MEASUREMENT APPARATUS     Apparatus used   How it is used   Electronic Balance   ● Values are given at 2 d.p.   ● Mini glass enclosure around the balance to prevent   wind from affecting measurements   Measuring Cylinder   ● Approximate measurements   ● 1cm ​ 3 ​ to 1000cm ​ 3 ​ or more   Burette   ● Accurate measurements to 0.05cm ​ 3   ● Measure up to 50cm ​ 3   Volumetric flask   ● Very accurate   3

● Used to measure fixed volumes   ● Used to prepare standard solutions of exact   concentration   Syringe   ● Small syringe → small volume of liquids   ● Large syringe → large volume of gases     TAKING MEASUREMENTS   Take the reading of a liquid at the bottom of the meniscus.       WHY DO WE NEED TO COLLECT GASES?   Gases allow us to determine the rate and progress of a reaction.     METHODS OF COLLECTING GASES   Considerations to be made:   ● Density (compared to the air)   ● Solubility (in water)   4

Methods   Diagram   When to be used   Displacement of   water     For gases which are   insoluble in water     ● E.g. H ​ 2 ​ , O ​ 2 ​ , CO ​ 2   Upward delivery     For gases which are denser   in the air (and soluble in   water)   ● E.g. Cl ​ 2   Downward   delivery     For gases which are less   dense than air (and soluble   in water)   ● E.g. NH ​ 3 ​ , H ​ 2   5

Gas syringe     When there is a need to   monitor the rate of   evolution in a gas       HOW TO COLLECT DRY SAMPLES OF GAS     Properties of gas   Diagram   Acidic (e.g. Concentrated sulfuric   acid (H ​ 2 ​ SO ​ 4 ​ ) )     Alkaline (e.g. Calcium Oxide (CaO) )     6

Neutral (e.g. Fused Calcium   Chloride)         PROPERTIES OF COMMON GASES     Gas   Formula   Colour   Density (compared to   air)   Solubility in water   Ammonia   NH ​ 3   Colourless   Less dense   Extremely soluble   Carbon   Dioxide   CO ​ 2   Colourless   Denser   Slightly soluble   Chlorine   Cl ​ 2   Greenish-Yellow   Denser   Soluble   Hydrogen   H ​ 2   Colourless   Less dense   Insoluble   Hydrogen   Chloride   HCl   Colourless   Denser   Very soluble   Oxygen   O ​ 2   Colourless   Slightly denser   Slightly soluble   Carbon   Monoxide   CO   Colourless   Slightly denser   Slightly soluble   Nitrogen   N ​ 2   Colourless   Slightly denser   Insoluble   Sulfur dioxide   SO ​ 2   Brownish   Denser   Very soluble   Helium   He   Colourless   Less dense   Insoluble       7

PURIFICATION AND SEPARATION   WHAT IS A PURE SUBSTANCE?   ● A single substance that is not mixed with anything else   ● Fixed melting and boiling point   ● Only produces a single spot on a chromatogram     WHAT IS A MIXTURE?   ● Consists of 2 or more substances that are mixed (not chemically combined   together, can be separated)   ● An impure substance can be a mixture of more than 2 substances (e.g. water +   sand + silt)   ● Melts and boils over a range of temperatures   ○ The boiling point becomes higher   ○ The melting point becomes lower     PURITY IS IMPORTANT BECAUSE IT AFFECTS…   ● The extent of a reaction   ○ How far the reaction proceeds   ● The efficiency of a reaction   ● The efficacy of a chemical   ○ Efficacy ​ : the ability to produce the intended result   ● Price of a material       8

Separation techniques   DECANTING   Separates an ​ insoluble solid from a liquid ​ by pouring off the liquid from the container   carefully.   FILTRATION   Used to separate an ​ insoluble solid from a liquid ​ .   Apparatus:   ● Beaker   ● Filter funnel   ● Filter paper   Key terms:   ● Residue ​ : The solid left in the filter paper   ● Filtrate ​ : The liquid collected in the beaker   EVAPORATION TO DRYNESS   Separates ​ dissolved solids from a solution ​ .     Note: Some solids are not heat stable and will decompose when heated, even after   evaporation, and some impurities will still be present in the solution     Apparatus: Evaporating dish   CRYSTALLISATION   Separates a ​ dissolved solid from a solution ​ , forming ​ pure crystals ​ of the substance. The   filtrate has to be ​ saturated ​ before the flame is turned off. ​ Rinse the crystals ​ with cold   distilled water (to remove impurities).     The solubility of the solute decreases, leaving the extra solute that cannot remain   dissolved to be separated as crystals.   9

Apparatus:   ● Evaporating dish   ● Filter paper   ● Bunsen burner   ● Beaker   ● Filter funnel   ● Stirring rod   Key terms:   ● Filtrate ​ : Liquid collected in the beaker   after filtration   ● Solvent ​ : Liquid in mixture along with   solvent   ● Crystals ​ : Pure solids obtained   ● Impure solid ​ : Solid in mixture along   with solvent   ● Solute ​ : The substance dissolved in a   given solution   Example of substances that can crystalise:   ● The crystallisation of Copper (II)   sulfate solution   SUBLIMATION   Used to separate ​ a mixture of solids ​ , one of which ​ sublimes ​ .   Key terms:   ● Sublime ​ : The change of state from the solid state to the   gaseous state   Example of substances that can sublime:   ● Iodine found in a mixture of iodine and sand will sublime   when heated. Ammonium compounds can also sublime.   10