Shared Flashcard Set

Details

Edexcel Unit 1
Edexcel A-Levels Unit 1 notes
90
Chemistry
12th Grade
05/21/2013

Additional Chemistry Flashcards

 


 

Cards

Term
Cations, X+...
Definition

Most singular ions, Na+...

Only NH4+ applicable

Term
Anions , X-...
Definition

Most molecular/compound ions, NO3-...

Cl-, Br-,I-, O2-

Term

Soluble Anions

NO3-, Cl-, Br-, I-, SO4-2

 

Definition

Insoluble with

Ag+ Pb+2 ...

Term

Insoluble Anions


OH- S-2 CO3-2 PO4-3

Definition

Soluble with


Na+ KNH4+(except OH-) Ba+(only OH-)

Term
Relative Atomic Mass
Definition
Average mass of one atom of the element as compared to 1/12 mass of one atom of C-12
Term
ppm
Definition

1 ppm = 1 mg/dm3


= 1 x 10-3 g of substance

1 dm3 of solution

Term
% yield
Definition

    actual    

theoretical

 

x 100%

Term
Yield < 100 %
Definition

1. XXX reactants not pure

2. Loss of XXX products during transfer

3. XXX side reaction occurs

4. XXX reaction does not reach completion.

Term
Atom Economy
Definition

           Molecular Mass of Desired Product         

Sum of Molecular Mass of all reactants/products

 

x 100

Term
Exothermic Reaction
Definition

1. Enthalpy of Products < Enthalp of Reactants

2. -ve Enthalpy Change

3. High Temperature

4. Heat lost to surroundings

5. Bonds formed

 

[image]

 

Term
Endothermic Reaction
Definition

1. Enthalpy of Products > Reactants

2. +ve Enthalpy Change

3. Lower Temperature

4. Gain from surroundings

5. Bonds broken

[image]

Term
Thermodynamic Stability
Definition
Lower = More Stable
Term
Standard Enthalpy of Formation
Definition

Keywords


1 mole of compound

From its elements

Standard states at 298K and 1 atm

 

Term
Standard Enthalpy of Combustion
Definition

1 mole of substance

Burns completely in oxygen

at 298K and 1 atm

Term
Standard Enthalpy Change of Neutralisation
Definition

1 mole of water is formed

From neutralisation of 1 acid by 1 alkali

at 298K and 1 atm

Term
Standard Enthalpy Change of Atomisation
Definition

1 mole of separate gaseous atoms

From element in its standard state

at 298K and 1 atm

Term
Bond Enthalpy
Definition

Break 1 mole of covalent bond

in gaseous molecules

Term

Experimental method to find Enthalpy Change

 

Calorimeter

Definition

- M x C x ΔT

- Only use mass of solution and solution's C as substance/powder etc. have negligible C and M

Term
Possible errors in using calorimeter to measure Enthalpy Change of Neutralisation
Definition

1. Heat lost to calorimeter.

2. Assumption density and specific heat capacitry of solution same as water.

Term
Calorimeter - Why Polystyrene cup and not beaker?
Definition

1. Reduces heat lost.

2. Inert/ Does not react with most chemicals.

3. Does not absorb much heat.

4. If use beaker, ΔH will decrease.

Term
Enthalpy Change of Combustion of fuel
Definition

Black solid - Carbon, formed due to incomplete combustion

 

Term

Experimental of Combustion < Theoretical

 

1. Heat lost to surroundings

2. Some heat goes to beaker instead

3. Incomplete combustion due to inadequate O2

4.Condition of products not standard (water vapour, endothermic reaction)

Definition

Resolutions

 

1. Use shields

2. Use copper tin

3. No shields

Term
Why excess substances?
Definition

To ensure all XXX have completely reacted

 

OR

 

To ensure all XXX have neutralised completely (if neutralisation)

Term
Hess's Law Cycle
Definition

If using enthalpies of formation,

1. Arrows go up

2.  Elements as middle part

 

If using enthalpies of combustion,

1. Arrows go down

2. Combustion products as middle part

Term

Why XXX reaction cannot be determined directly but calculated through Hess's Law?

 

(Alkene to alkane)

 

CnH2n + H2 -> CnH2n+2

Definition

1. Reaction cannot be conducted in lab due to H2 being flammable

2. Ethane etc. may undergo combustion

3. Reaction rate is too slow.

Term

Bonds broken +ve

 

Definition
Bonds formed -ve
Term
3 uses of Table of average standard bond enthalpies
Definition

1. Compare strength of bonds

2. Understand struscture and bonding

3. Calculate ΔHf and ΔHreaction
using Hess's Law

Term
Ensuring accuracy of experiments
Definition

1. Constant stirring of water to ensure even temperature

2. Use screen/coppertin/polystyrene board/lid etc to prevent heat loss

3. Use more accurate apparatus (thermometers that read up to 0.1, use pipetter not measuring cylinder...)

4. Take temperature every 30s...

Term
Percentage Error
Definition

        Uncertainty of Error     

Value of measurement

 

x 100

Term
Increase...
Definition

Reliability : repeat experiment and get average value

 

Accuracy :

1. Use precise instruments

2. Use larger volume/mass...

Term
Which sub-atomic particle would deviate the most?
Definition
Electron as it has a lower mass than proton.
Term

Isotopes

 

1.Same Chemical properties

2.Different Physical properties

 

Definition

1. same amount of electrons/electronic configuration

2. Masses are different

Term
Mass Spectrometer
Definition

1. Vaporisation (gaseous atoms to move through instrument)

2. Ionisation (bombarded by high energy electrons and 1 electron is knocked out of atom)

3. Acceleration (Electric field)

4. Deflection (Magnetic field according to m/z ratio)

5. Detection (shows how many ions of each m/z ratio in sample)

Term
Usage of mass spectrometry
Definition

1. Archeology - Radiocarbon dating using C-14

2. Geographical - Detect oil composition

 

...

Term
Subshells
Definition
s, p, d, f
Term

Atomic Radii

 

1.Decrease across Period

2.Increase down Group

 

Definition

1. More protons but electrons in same energy level/shells, force of attraction increase

 

2. More protons but electron in higher energy levels, outermost electrons more shielded, force of attraction decreases

Term
Ionisation energy
Definition

Remove 1 mole of electrons

From 1 mole of gaseous atoms

to form 1 mole of gaseous positive ions

Term
Factors of Ionisation energy
Definition

1. Distance from nucleus (atomic radii)

2. Nuclear charge (number of protons)

3. Shielding effect (by inner shell electrons)

Term

Trends in first ionisation energy

 

1. Increase across period

2. Decrease down the group

Definition

1. Atomic radius smaller, Nuclear charge increases, Negligible shielding as all in same shell, FOA ↑

 

2. Atomic radius increase but cancelled off by increase in number of protons, but shielding effect increase, FOA decrease

Term
First ionisation energies do not increase smoothly across period
Definition
Due to presence of subshells
Term
First Electron Affinity
Definition

1 mole of electrons

Added to 1 mole of atoms

In gaseous state

Term

First EA

 

1. Increase across period

 

Definition
1. Nuclear charge increase, atomic radius smaller,negligible shielding
Term
Why first EA always exothermic and why second EA endothermic?
Definition

1. To form an attraction between incoming electrons and nucleus

2. Repulsion between incoming electron and negative ion

Term
Ionic Bonding
Definition
Electrostatic force of attraction between oppositely charged ions
Term
Giant Ionic Lattic Structure
Definition

1. Neatly arranged

2. Very high melting & boiling pt. - large amount of energy to overcome strong electrostatic attractions and separate ions

3. Hard but brittle - Any dislocation=layers moving=repulsion occurs=splits crystal

4. Good electrical conductivity in molten or aqueous state only - solid=ions held strongly by lattice, liquid/molten=mobile ions & conduction takes place

5. Very high density - higher than water but lower than typical metals

Term
3D arrangement of ions in NaCl
Definition

6 Na+ ion around each Cl- ion

 

OR

 

Cubic structure with alternate Na+ and
Cl- ions

Term

Size of cation

 

1. < size of atom

 

Definition
1. Number of electron shell decreases, higher p/e ratio, Effective nuclear charge increases, remaining e- are pulled in closer to nucleus
Term

Size of Anion

 

1. > Size of Atom

2. Increases down the group

Definition

1. Same number of electron shell but p/e ratio decreases, Effective nuclear charge decreases, expansion of electron cloud

 

2. Number of protons increases, but electrons in higher/outer shell, more shielding, FOA decreases

Term
Isoelectronic ions
Definition

Ions with same number of electrons

 

H- Li+ Be2+ B3+   - 2 electrons in each ion

Term
Lattice Energy
Definition

1 mole of ionic compound

formed from gaseous ions under standard conditions

Term
Factors
Definition

1. larger ionic charge = larger lattice energy

2. smaller sum of ionic radii=larger lattice energy

Term
Determination of Lattice energy
Definition
Born=Haber Cycle
Term
Chances of formation
Definition
higher when amount of energy released high
Term
Polarisation in ionic bonds
Definition

Cations - larger charge= higher polarising power

 - smaller redius = higher polarising power

 

Anions - larger radius= higher polarisability

Term
Why CaI2 more covalent than KI? (Why more difference between theoretical and experimental lattice energy?)
Definition

-higher charge, smaller radius

-more polarising

-able to distort electron cloud to a greater extent

Term

Covalent Bonding

 

Definition
Electrostatic force of attraction between the nuclei and shared pair of electrons
Term
Dative Covalent Bonds
Definition
Shared pair of electrons which has been provided by one of the bonding atoms
Term
Metallic Structure
Definition
A giant lattice of positive metal ions fixed in position and surrounded by a sea of electrons
Term
Metallic Bonding
Definition
Force of attraction between the positive metal ion and negative delocalised electrons
Term
Factors on strength of metallic bond
Definition

1. Ionic radius

2. Ionic charge

3. Valence electrons (number of delocalised electrons)

Term

Physical properties of Giant Metallic Lattices

 

1. V.high melting and boiling pt.

2. Good malleability and ductility

3. Good electrical conductivity in both solid and molten states

4. V.high density

Definition

1. Strong electrostatic attractions between cations and delocalised electrons

2. Ions and delocalised electrons move around each other, will not break as cations still surrounded by electrons

3. Delocalised electrons free to move and can conduct electricity when a potential difference is applied

4. Higher than water and ionic compound

Term
Why strength of bond between simple molecules/simple atoms weak?
Definition
weak Van der Waals forces between molecules/atoms
Term
Isomers
Definition

1. Structural - same molecular formula but different structure

 

2. Geometrical -restricted rotation of Carbon-Carbond double bond(C=C)

- Both C atoms of C=C must have 2 different groups/atoms

Term

Cis/trans isomers

 

- must have at least 1 same group of atoms each side

Definition

Cis - same group of atoms at same side of C=C

 

Trans - Groups at different sides

 

Limits - When all different groups, don't work

Term
E-Z isomerism
Definition

Use mass instead (group with higher mass is used)

 

E- Different

Z - Same

Term
Alkanes
Definition

1. CnH2n+2

2. Only single bonds

3. 4 H bonds to every C atom

4. Saturated Hydrocarbon

Term
Fractional distillation (of crude oil)
Definition

1. Higher = not so pure, lower boiling/melting point

2. Middle area purest

3. Lowest= bitumen, Highest=Gas,

 

Gas<Petrol<Chemicals<Aircraft fuel<Central Heating fuel<Lube<Power Station/Ship fuel<Candles and grease<Road

Term
Cracking
Definition

Use of high temperature or catalyst to break large hydrocarbon to smaller molecules of alkane/alkene

 

C-C bonds broken

 

(Can also occur when no oxygen present)

 

E.g of catalyst zeolite Al2O3

Term
Why short chains high in demand?
Definition

1. Small chain of alkane allow for use as fuel

2. Small chain of alkene for use in polymer production

Term
Catalytic Reforming
Definition
Process in which straight-chain alkanes form rings or branched chains in presence of high temperature or catalyst(E.g. Pt)
Term
Alkane reactions
Definition

1. Combustion of alkanes

2. Free radical substitution (E.g with Cl2) (must have UV)

Term
Bond fission
Definition

1. Homolytic

2. Heterolytic

Term
Alkene
Definition

1. CnH2n

2. C=C

3. Unsaturated hydrocarbon

4. More reactive than alkane

5. Can form cis-trans (E/Z) isomers

Term
Nature of C=C
Definition
Consists of 1 σ (sigma) and 1 ∏ (pi) bonds
Term
σ bond
Definition

1. Overlap of 2 s-orbitals

2. Overlap of 2 p-orbitals (one end to another end)

3. Overlap of one s-orbital and p-orbital

Term
∏ bond
Definition
Side-on overlap of 2 p-orbitals (at 2 points)
Term
σ stronger than ∏
Definition
Sigma bond overlaps are closer to nuclei
Term
C=C - region of high electron density
Definition
Electrons more diffused and less firmly held. So easily attacked by electrophiles.
Term
Chemical reactions of alkene
Definition

1. Combustion

2. Electrophilic addition

3. Oxidation

4. Polymerisation

Term
Electrophilic addition
Definition
Type of reaction in which an electrophile is attracted to the electron density in the C=C and added across the double bond to form one product.
Term

Markovnikov's rule

 

(My understanding of it)

Definition
The more hydrogen atoms attached to the carbon atoms of the double bond(reactant) in the product, the more likely it is to be the major product. (more stable)
Term
Test for C=C bond (double bond)
Definition

Add few drops of Bromine water, Brto alkene.

 

It will be decolourised from brown to colourless.

Term
Polymerisation
Definition
Process in which many small molecules (monomers) join together into large molecules (polymers) consisting of repeating units
Term
Addition Polymerisation
Definition
alkene monomers are joined together without elimination of any atoms/molecules
Term
General Equation
Definition

[image]

 

Term
Common polymers
Definition

1. Polyethene - food wrap

2. Polypropene - yogurt tubs

3. Polybutene - Rubber piping

4. Polychloroethen (PVC) - Cable insulation

      -Make flexible using plasticizer to allow chains to slide

5. Polytetrafluoroethene (Teflon) - Non-stick coating on frying pan

6. Polyphenylethen (Polystyrene) - Foam packaging, polystyrene cup

Term
Polymer Problems
Definition

1. Use non-renewable resources (from crude oil)

2. High-energy production costs

3. Non-biodegradable - landfill problem

4. Does not burn easily (requires extremely high heat)

Term
Solutions
Definition

1. Reducing

2. Recycling

3. Burn waste (Produces energy)

4. Feedstock (Convert waste to hydrocarbon)

5. Biodegradable polymers (made from natural polymers - starch, cellulose)

Term
Energy Recovery
Definition
Reducing energy consumption of polymer manufacture
Supporting users have an ad free experience!