Edexcel Unit 1 – Flashcards

Unlock all answers in this set

Unlock answers
question
Cations, X+...
answer

Most singular ions, Na+...

Only NH4+ applicable

question
Anions , X-...
answer

Most molecular/compound ions, NO3-...

Cl-, Br-,I-, O2-

question

Soluble Anions

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

 

answer

Insoluble with

Ag+ Pb+2 ...

question

Insoluble Anions


OH- S-2 CO3-2 PO4-3

answer

Soluble with


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

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

1 ppm = 1 mg/dm3


= 1 x 10-3 g of substance

1 dm3 of solution

question
% yield
answer

    actual    

theoretical

 

x 100%

question
Yield < 100 %
answer

1. XXX reactants not pure

2. Loss of XXX products during transfer

3. XXX side reaction occurs

4. XXX reaction does not reach completion.

question
Atom Economy
answer

           Molecular Mass of Desired Product         

Sum of Molecular Mass of all reactants/products

 

x 100

question
Exothermic Reaction
answer

1. Enthalpy of Products < Enthalp of Reactants

2. -ve Enthalpy Change

3. High Temperature

4. Heat lost to surroundings

5. Bonds formed

 

[image]

 

question
Endothermic Reaction
answer

1. Enthalpy of Products > Reactants

2. +ve Enthalpy Change

3. Lower Temperature

4. Gain from surroundings

5. Bonds broken

[image]

question
Thermodynamic Stability
answer
Lower = More Stable
question
Standard Enthalpy of Formation
answer

Keywords


1 mole of compound

From its elements

Standard states at 298K and 1 atm

 

question
Standard Enthalpy of Combustion
answer

1 mole of substance

Burns completely in oxygen

at 298K and 1 atm

question
Standard Enthalpy Change of Neutralisation
answer

1 mole of water is formed

From neutralisation of 1 acid by 1 alkali

at 298K and 1 atm

question
Standard Enthalpy Change of Atomisation
answer

1 mole of separate gaseous atoms

From element in its standard state

at 298K and 1 atm

question
Bond Enthalpy
answer

Break 1 mole of covalent bond

in gaseous molecules

question

Experimental method to find Enthalpy Change

 

Calorimeter

answer

- M x C x ?T

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

question
Possible errors in using calorimeter to measure Enthalpy Change of Neutralisation
answer

1. Heat lost to calorimeter.

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

question
Calorimeter - Why Polystyrene cup and not beaker?
answer

1. Reduces heat lost.

2. Inert/ Does not react with most chemicals.

3. Does not absorb much heat.

4. If use beaker, ?H will decrease.

question
Enthalpy Change of Combustion of fuel
answer

Black solid - Carbon, formed due to incomplete combustion

 

question

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)

answer

Resolutions

 

1. Use shields

2. Use copper tin

3. No shields

question
Why excess substances?
answer

To ensure all XXX have completely reacted

 

OR

 

To ensure all XXX have neutralised completely (if neutralisation)

question
Hess's Law Cycle
answer

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

question

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

 

(Alkene to alkane)

 

CnH2n + H2 -; CnH2n+2

answer

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

2. Ethane etc. may undergo combustion

3. Reaction rate is too slow.

question

Bonds broken +ve

 

answer
Bonds formed -ve
question
3 uses of Table of average standard bond enthalpies
answer

1. Compare strength of bonds

2. Understand struscture and bonding

3. Calculate ?Hf and ?Hreaction
using Hess's Law

question
Ensuring accuracy of experiments
answer

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...

question
Percentage Error
answer

        Uncertainty of Error     

Value of measurement

 

x 100

question
Increase...
answer

Reliability : repeat experiment and get average value

 

Accuracy :

1. Use precise instruments

2. Use larger volume/mass...

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

Isotopes

 

1.Same Chemical properties

2.Different Physical properties

 

answer

1. same amount of electrons/electronic configuration

2. Masses are different

question
Mass Spectrometer
answer

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)

question
Usage of mass spectrometry
answer

1. Archeology - Radiocarbon dating using C-14

2. Geographical - Detect oil composition

 

...

question
Subshells
answer
s, p, d, f
question

Atomic Radii

 

1.Decrease across Period

2.Increase down Group

 

answer

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

question
Ionisation energy
answer

Remove 1 mole of electrons

From 1 mole of gaseous atoms

to form 1 mole of gaseous positive ions

question
Factors of Ionisation energy
answer

1. Distance from nucleus (atomic radii)

2. Nuclear charge (number of protons)

3. Shielding effect (by inner shell electrons)

question

Trends in first ionisation energy

 

1. Increase across period

2. Decrease down the group

answer

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

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

1 mole of electrons

Added to 1 mole of atoms

In gaseous state

question

First EA

 

1. Increase across period

 

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

1. To form an attraction between incoming electrons and nucleus

2. Repulsion between incoming electron and negative ion

question
Ionic Bonding
answer
Electrostatic force of attraction between oppositely charged ions
question
Giant Ionic Lattic Structure
answer

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

question
3D arrangement of ions in NaCl
answer

6 Na+ ion around each Cl- ion

 

OR

 

Cubic structure with alternate Na+ and
Cl- ions

question

Size of cation

 

1. < size of atom

 

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

Size of Anion

 

1. > Size of Atom

2. Increases down the group

answer

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

question
Isoelectronic ions
answer

Ions with same number of electrons

 

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

question
Lattice Energy
answer

1 mole of ionic compound

formed from gaseous ions under standard conditions

question
Factors
answer

1. larger ionic charge = larger lattice energy

2. smaller sum of ionic radii=larger lattice energy

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

Cations - larger charge= higher polarising power

 - smaller redius = higher polarising power

 

Anions - larger radius= higher polarisability

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

-higher charge, smaller radius

-more polarising

-able to distort electron cloud to a greater extent

question

Covalent Bonding

 

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

1. Ionic radius

2. Ionic charge

3. Valence electrons (number of delocalised electrons)

question

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

answer

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

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

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

question

Cis/trans isomers

 

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

answer

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

 

Trans - Groups at different sides

 

Limits - When all different groups, don't work

question
E-Z isomerism
answer

Use mass instead (group with higher mass is used)

 

E- Different

Z - Same

question
Alkanes
answer

1. CnH2n+2

2. Only single bonds

3. 4 H bonds to every C atom

4. Saturated Hydrocarbon

question
Fractional distillation (of crude oil)
answer

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

question
Cracking
answer

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

question
Why short chains high in demand?
answer

1. Small chain of alkane allow for use as fuel

2. Small chain of alkene for use in polymer production

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

1. Combustion of alkanes

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

question
Bond fission
answer

1. Homolytic

2. Heterolytic

question
Alkene
answer

1. CnH2n

2. C=C

3. Unsaturated hydrocarbon

4. More reactive than alkane

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

question
Nature of C=C
answer
Consists of 1 ? (sigma) and 1 ? (pi) bonds
question
? bond
answer

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

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

1. Combustion

2. Electrophilic addition

3. Oxidation

4. Polymerisation

question
Electrophilic addition
answer
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.
question

Markovnikov's rule

 

(My understanding of it)

answer
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)
question
Test for C=C bond (double bond)
answer

Add few drops of Bromine water, Brto alkene.

 

It will be decolourised from brown to colourless.

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

[image]

 

question
Common polymers
answer

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

question
Polymer Problems
answer

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)

question
Solutions
answer

1. Reducing

2. Recycling

3. Burn waste (Produces energy)

4. Feedstock (Convert waste to hydrocarbon)

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

question
Energy Recovery
answer
Reducing energy consumption of polymer manufacture
Get an explanation on any task
Get unstuck with the help of our AI assistant in seconds
New