QCE Chemistry Unit 3 and 4

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Forward Reaction

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112 Terms

1

Forward Reaction

A reaction between reactants to form products

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2

Reverse Reaction

The backwards reaction in which the products react to re-form the reactants. If a reaction is reversed the products of the forward reaction now becomes the reactants of the reverse reaction.

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3

Dynamic Equilibrium

The state a reaction reaches when the rates of the forward and reverse reactions are equal.

Occurs when:

  • the reaction is incomplete: does not only consist of products

  • Bonds are being broken and re-formed

  • The rate of the forward and reverse reaction is equal

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4

Le Chateliers Principal

If a system is subjected to a change, the system will adjust to partially oppose the change. Only temperature and concentration can change the position of equilibrium.

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What does a large Kc mean?

The system contains more product than reactant

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What does a small Kc mean?

The system contains more reactant than product

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Acids

When dissolved in water they donate hydrogen ions. Different acids can donate different amounts of hydrogen.

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Strong Acid

Completely ionises in H2O

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Weak Acid

doesn’t completely ionise in H2O

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10

Brønsted-Lowry Acids and Bases

Acids donate protons (H+) while bases accept protons (H+).

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Strong Acid Examples

  • HCl (hydrochloric)

  • HNO3 (nitric)

  • H2SO4 (sulfuric)

  • H3PO4 (phosphoric)

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Strong Bases Examples

  • NaOH (sodium hydroxide)

  • KOH (potassium hydroxide)

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Weak Acid Examples

  • H2CO3 (carbonic)

  • CH3COOH (Ethanoic)

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Weak Base examples

  • NH3 (ammonia)

  • Amines

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Buffers

A solution that resists changes in pH when small amounts of acids or alkalies are added

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Burette

A graduated glass that dispenses highly accurate volumes of a standard solution

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Titrant

The standard solution in a burette that is added to an unknown concentration

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Titre

The volume of solution dispensed from a burette

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Aliquot

A fixed volume of liquid measured by a pipette

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Titrand

A solution whose concentration is determined by titration

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Analyte

A solution of unknown concentration

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Concordant titres

Volumes of standard solution dispensed from a burette that differ by only 0.1mL from highest and the lowest

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Strong acid and strong base (titration curve)

  • The pH starts low

  • pH ends high

  • equivalence point is at a pH of 7

  • initially pH changes slowly

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Weak acid and strong base (titration curve)

  • the pH starts high (2-4)

  • the pH ends high

  • pH rises quickly initially then slows

  • equivalence point is above pH 7

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Weak base and strong acid (titration curves)

  • pH starts high (10-12)

  • the pH ends low

  • pH falls quickly then slows

  • equivalence point below pH 7

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Redox

A chemical reaction involving the transfer of electrons from one reactant to another

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Oxidation

a loss of electrons

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Reduction

A gain of electrons

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Oxidising agent

a reactant that causes another reactant to lose electrons and be oxidised and itself reduced

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Reducing agent

a reactant that causes another reactant to gain electrons and itself be oxidised

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Ionisation Energy

The energy required by a gaseous atom to remove an electron from its valence shell

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Redox of non-metals

Accept electrons more easily are stronger oxidising agents

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Electronegativity

The attraction between a positively charged nucleus and the negatively charged electrons of a neighbouring atom

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Single Displacement

A chemical reaction in which a more reactive metal ion replaces a reactive metal ion in a molecule

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Steps to balancing a Redox equation

  1. Write skeleton equation half equations

  2. Balance atoms except H and O

  3. Use water to balance O

  4. Use H+ to balance H

  5. Use e- to balance charge

  6. Balance electrons

  7. Add half equations

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36

Galvanic cells

An electrochemical cell in which the reduction and oxidation half-equations are separated and connected through a circuit to generate electricity

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Primary Cell

A non-rechargeable battery. A type of galvanic cell that produces an electrical current

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Fuel Cell

A galvanic cell that produces electricity by using a constant supply of reactants and inert electrodes that don’t break down

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Electrolytic cell

A cell that uses an external electrical potential difference to provide the energy for non-spontaneous redox reactions to occur

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40

Alkane

Contains single bonds between carbon atoms

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41

Alkene

Contains one or more double bonds between carbon atoms

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Alkyne

Contains one or more triple bond between carbons

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Stereoisomers

Two or more organic compounds that have the same atoms and bonding but a different spatial scale. Has the same formula but a different atom arrangement.

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Geometric isomers

Two organic compounds that have different arrangements of atoms around a rigid double bond. Cis and Trans structures

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Enantiomers

Have an asymmetrical carbon with four different substituents covalently bonded. Are mirror images and non-superimposable

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Cis structures

Have similar substituents on the same side of the double bond

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Trans structures

Similar substituents on opposite sides of the double bond

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Primary Alcohol

Alcohol in which the hydroxyl is bonded to one other carbon

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Secondary Alcohol

An alcohol in which the the carbon bonded to the hydroxyl is bonded to two other carbons

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Tertiary Alcohol

An alcohol in which the the carbon bonded to the hydroxyl is bonded to three other carbons

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Haloalkanes

Contains a halogen substituent (Cl, F, Br, I)

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Aldehyde

Has a carbonyl group at the end of the main chain

suffix -al

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Ketone

Has a carbonyl group within the main chain

has the suffix -one

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Carboxylic acid

contains a carbonyl functional group

COOH group becomes the main chain

Carboxyl carbon is carbon 1

Suffix -oic acid

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Ester

Contains a carbonyl attached to an oxygen

Derived from a carboxylic acid and an alcohol

First part is the alcohol

Second is the carboxylic acid

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Amine

Contains a nitrogen atom bonded to three other groups either hydrogen or alkyl groups

suffix -amine

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Amide

Contains amine and carbonyl functional groups adjacent to each other

Use N to represent nitrogen in complex molecules

suffix -amide

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58

X-ray crystallography

Technique used to determine the atomic and molecular structure of crystals by analyzing the diffraction pattern of X-rays passing through the crystal. Will give information on bond angles, distance between atoms, and the number of electrons.

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Mass Spectrometry

Analytical technique that measures the mass-to-charge ratio of ions, providing information about the composition and structure of molecules. Can be solid, liquid, or gas.

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60

Alcohols (Infrared spectroscopy)

  • O-H peak

  • 3200-3600Cm

  • Looks like a tongue

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Sword (infrared spectroscopy)

  • C=O peak

  • 1700-1750Cm

  • indicates aldehydes, ketones, esters, carboxylic acids

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Carboxylic acids (infrared spectroscopy)

  • O-H peak

  • whole left hand side of the graph in size

  • looks like a combination between a hairy beard and a sword

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C-O (Infrared spectroscopy)

  • around 1400cm

  • indicates alcohols and esters

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Border (infrared spectroscopy)

  • C-H peak

  • 3000 cm

  • below 3000 is alkanes

  • above 3000 is alkenes

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Triple bond (infrared spectroscopy)

  • C (t-bond) C and C (t-bond) N peaks

  • Low 2000cm

  • indicates nitrile and alkynes

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W-peak (infrared spectroscopy)

  • N-H peak

  • 3300-3500cm

  • indicates amines

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Chromatography

The rate of movement depends on how strongly the component absorbs onto the stationary phase and how readily the component dissolves in the mobile phase

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Electrophoresis

Technique that separates molecules based on their size and charge using an electric field. Higher charges move faster

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69

Addition Reactions

Atoms add across a double bond or triple bond in an unsaturated hydrocarbon. Multiple bond breaks as two substituents are added.

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Hydrogenation

  • Addition of a hydrogen

  • metal catalyst required (Pt)

  • Adds hydrogen atom to each carbon of the multiple bond

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Halogenation

  • Addition of a halogen

  • No condition

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72

Hydrohalogentaion

  • Addition of a hydrohalide

  • no conditions

  • 90% Markovnikov product

  • 10% anti-Markovnikov product

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Hydration

  • Addition of water

  • Two substituents are hydrogen and a hydroxyl group

  • produces an alcohol

  • requires high temperature and pressure and a strong acid catalyst

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Polymerisation

  • Successive addition of alkene monomers

  • Initial hydrocarbon is the monomer

  • self-addition reaction

  • requires heat, high pressure, catalyst

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Elimination

  • Removal of substituents from carbon atoms in a haloalkane

  • Requires heat under reflux, concentrated solution of sodium hydroxide or potassium hydroxide in ethanol

  • Tertiary and secondary haloalkanes

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Substitution of Alkanes

  • Haloalkanes are formed by reaction of alkanes with halogens

  • requires UV light, temps of around 200C

  • leftover hydrogen and halogen from hydro-halide by-product

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Substitution of Haloalkanes

  • Carbon-halogen bond is polar

  • Susceptible to substitution by reagents with non-bonding pair of electrons

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Oxidation (organic reactions)

The loss of electrons, loss of hydrogen atoms and the gain of oxygen

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Oxidation of primary alcohols

  • Contains -Ch2OH group

  • loss of 2 hydrogens to form an aldehyde

  • further oxidation to a carboxylic acid through a gain of O2

  • requires warm, acidified potassium dichromate

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Oxidation of secondary alcohols

  • contains -CHROH group

  • loss of two hydrogens to form a ketone

  • requires warm acidified potassium dichromate

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Alcohols and Alkanes through combustion

Involves exothermic burning of fuel in excess oxygen to produce CO2 in H2O

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Reduction (organic reactions)

Gain of electrons, gain of hydrogen atoms, loss of oxygen

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Reduction of Alkenes

  • Hydrogen added increasing the saturation

  • requires high temperature, H2 gas, a metal catalyst

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Reduction of Nitriles

  • Reduced to primary amines

  • requires a metal reagent

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Enzymes

  • Proteins that catalyse reactions

  • Active sites for one substrate

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Structure of a protein

  • Hydrophobic-folding amino acids within the chain

  • non-polar amino acids

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Amino Acids

  • A monomer of protein that has both an amino and carbonyl croup

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Zwitterion

A molecule that has separately positively and negatively charged parts

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Synthetic polymer use

  • Strong

  • Varying density

  • Lack of reactivity

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90

HDPE

  • Polymer made from ethene, with a high strength-to-density ratio

  • produced at low temp and pressure'

  • no branches

  • high melting point

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LDPE

  • A polymer made from the monomer ethene with a low strength-to-density ratio

  • produced under high pressure and heat

  • many branches

  • typically amorphous and transparent

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Addition polymers

  • formed by addition polymerisation

  • commonly used in plastic bags and bottles

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Lipids

  • Polymers with low melting points

  • insoluble in water

  • also known as fats

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Fatty Acids

  • Carboxylic acid that has a long hydrocarbon chain

  • melting point increase with length of carbon chain

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Triglycerides

  • Prevents water loss

  • store fat

  • three fatty acids and glycerol

  • are large esters

  • can be saturated or unsaturated

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96

Saponification

  • also known as base hydrolysis

  • boiling animal fat or plant oil with excess aqueous sodium hydroxide

  • produces glycerol and 3 fatty acid salts (soap)

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Soap

  • Small hydrophilic head

  • large hydrophobic tail

  • head dissolves in water due to polar interactions

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98

Glucose

  • Alpha and beta configurations

  • Alpha has vertical bond to hydroxyl

  • beta has upward diagonal bond to hydroxyl

  • beta is less crowded

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99

Monosaccharides

  • Single sugar monomers

  • consist of a carbon chain with several hydroxyl groups and either a ketone or aldehyde functional group

  • have glycosidic linkage

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Disaccharide

  • Made from two monosaccharides in a condensation polymerisation reaction

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