Everything I didn't know from PMT

What is relative atomic mass

the mean weighted mass of an atom of an element compared with 1/12th the mass of an atom of carbon-12

What is relative molecular mass

the mean weighted mass of a molecule compared with 1/12th the mass of an atom of carbon-12

What is relative formula mass

the sum of the mean weighted masses of all atoms in the formula of a compound compared with 1/12th the mass of an atom of cabron-12

What is relative isotopic mass

the mass of an atom isotope compared with 1/12th the mass of an atom of carbon-12

What is a mole

the amount of substance containing as many particles as there are atoms in 12g of carbon-12.

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1 mole = 6.02 x 10^23 items

how is % yield calculated

how is % composition by mass calculated

how is a standard solution prepared from a concentrated solution

* a certain volume of the concentrated solution is added to a volumetric flask in order to get the desired final volume
* distilled water is added to the volumetric flask up to the line on its neck

What are orbitals

regions in the space around an atom where electrons are most likely to be found, they can contain a maximum of two electrons

How are e- arranged in orbitals

* electrons fill from the lowest energy orbital first
* electrons will prefer to occupy orbitals by themselves, and will only pair with other electrons if no other lower energy orbitals are available to fill

How are orbitals filled on the energy level diagram drawn

What did the Geiger-Marsden experiment show

it showed that the atom contained a very small, dense, positive nucleus

What is fusion

when two lighter nuclei collide and combine to form a heavier nucleus, releasing energy

Why do giant covalent lattices have a much greater melting point than simple covalent molecules

the covalent bonds between the atoms in a covalent lattice are much stronger than the London forces between the simple covalent molecules

Why are ionic substances only conductive when dissolved

when ions are in a solid, they are unable to move so they cannot carry charge. dissolving the solid causes the ions to be mobile, so they are free to carry charge

Why do both covalent and ionic lattices have high melting points

both lattices contain atoms that have multiple strong bonds around them, these bonds take a lot of heat energy to break

All the bond angles

how do different numbers of bonded and lone pairs produce different shapes in molecules

lone pairs repel more than bonded pairs

How does bonding occur in an ionic lattice

the attraction between ions of different charges and the repulsion between ions of the same charge causes overall attraction in the lattice

what is first ionisation enthalpy

the enthalpy change that occurs when one mole of electrons is removed from one mole of gaseous atoms

why does first ionisation energy increase as we move across a period

the number of protons in the nucleus increases which increases the nuclear charge and thus the nuclear force felt by outer electrons it therefore takes more energy to remove them

what is the formula of a sulfate ion

what is the formula of a carbonate ion

what is the formula of an ammonium ion

what is the formula of a hydrogencarbonate ion

Why does first ionisation energy decrease down a group

* the number of shells in the atom decreases, which increases shielding of outer electrons from the nucleus
* the nuclear radius also increases
* both of these factors mean that the attractive nuclear force felt by the electron is smaller, so it takes less energy to remove outer electrons

How do the charge densities of group 2 ions affect the thermal stability of their carbonates

smaller ions with the same charge have higher charge densities and distort the carbonate ion, so that the compound will decompose at a lower temperature

how can we test for Fe2+ ions

* add OH- ions
* the green solution will form a green precipitate

how can we test for Fe3+ ions

* add OH- ions
* the yellow solution will form an orange precipitate

how can we test for Cu2+ ions

* add OH- ions
* the blue solution will form a blue precipitate

how can we test for NH4+ ions

* add NaOH (aq) to a boiling tube containing the NH4+ ions
* warm the boiling tube
* any vapours given off by the tube will turn damp red litmus paper blue if NH4+ ions are present

how can we test for Al3+ ions

* add OH- ions
* the colourless solution will form a white precipitate

What should you add before adding AgNo3 in halide tests

* add a few drops of HNO3
* shake the test tube

how can we test for SO4 2- ions

* add Ba2+ ions
* a white precipitate should form

how can we test for CO3 2- ions

* add dilute nitric acid
* if effervescence occurs than CO3 2- ions are present

How can we test for

* Li+
* Na+
* K+
* Ca+

ions

* evaporate the water from the sample
* moisten a test wire and collect the solid residue from the evaporating dish
* pass this residue into a bunsen burner and record the colour of the flame

Flame test colour of: Na+

orange

Flame test colour of:Ca+

brick red

Flame test colour of: Li+

red

how can we test for Pb2+ ions

* add OH- ions
* a white precipitate will form
* upon adding excess OH- ions, the precipitate will dissolve

What’s an alkali

a species that releases OH- ions in solution

What’s a base

a soluble alkali

What is neutralisation

when the proton on an acid molecule is replaced by a metal ion (or ammonia), forming a salt and water

how do group 2 oxide react with water

MO + H2O --→ M(OH)2

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Group 2 oxides are therefore basic as they release OH- ions when dissolved

place the following in order of decreasing frequency:

Infra red

X-Rays

Microwaves

Gamma Rays

* Gamma Rays
* X-Rays
* Infra red
* Microwaves

What is volume measured in in the ideal gas equation

m^3

How can you predict the yield of a reaction

* work out the number of moles of a reactant you have used
* multiply by the ratio between the chosen reactant and product
* multiply by the Mr of the product

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what is the difference between a pi and a sigma bond

* a sigma bond is caused by the direct overlap of the p-orbitals of carbon atoms
* pi bonds are caused by the indirect ‘leaning’ overlap of p-orbitals

What is a double bond

consists of one pi bond and one sigma bond

what is the meaning of the term endothermic

* reactions that take energy in from the surroundings
* the energy needed to break the bonds is greater than the energy needed to make the bonds in the reaction

what is the meaning of the term exothermic

* reactions that release energy into the surroundings
* the energy needed to break the bonds is less than the energy needed to make the bonds in the reaction

what are standard conditions

* pressure: 100 kPa
* temperature: 298 K (room temp)
* all solutions: a concentration of 1 mol dm^-3 for electrode potentials

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define the standard enthalpy change of reaction

* the enthalpy change that occurs when species are reacted in the molar ratios as defined by a chemical equation
* the reaction takes place under standard conditions with reactants and products in their standard states

define the standard enthalpy change of combustion

the enthalpy change that occurs when a species is reacted with one mole of oxygen under standard conditions with products and reactants in their standard states

define the standard enthalpy change of formation

the enthalpy change that occurs when one mole of a compound is formed from its constituent elements in their standard states under standard conditions

define the standard enthalpy change of neutralisation

the enthalpy change that occurs when one mole of water is produced from a neutralisation that happens under standard conditions

What is average bond enthalpy

the energy needed to break one mole of the stated bond under standard conditions

what relation does bond enthalpy have to bond strength

* the greater the bond enthalpy, the greater the bond strength
* as the bond strength increases the length of the bond decreases

Is bond breaking exo or endo

endothermic

Is bond making exo or endo

exothermic

what does each term mean in q=mc△T

q= the energy absorbed by the material (normally water) in J

m= the mass of material being used in g

c= the specific heat capacity of the material used

△T= the change in temperature of the material

what is a catalyst poison

a substance that reduces the effectiveness of the catalyst by permanently bonding to the active sites

What does the heterogeneous catalyst look like

the reactants form partial bonds with the catalyst, adsorbing onto the surface, because the reactants are in close proximity, successful collisions are more frequent

What are some common simple molecular pollutants

* CO2, CO, NOx, SOx
* unburnt hydrocarbons

what are some methods of reducing co2 emissions

using renewable sources of electricity such as solar or wind power as well as using electric or hydrogen powered cars can be methods of reducing CO2 emissions

what are some methods to reduce CO and unburnt hydrocarbons

using more efficient engines and catalytic converters in cars

how can NOx and SOx emissions be reduced

modifications to engines and the fuels used can reduce NOx and SOx emissions

What's an aliphatic hydrocarbon

a hydrocarbon that does not contain any aromatic rings and is a straight or branched chain hydrocarbon

What is a functional group

a group of atoms on a carbon chain that gives the molecule its properties

Complete with conditions- H2C2H2 + H2O

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conditions:

H3PO4

300 degrees celcius

60 atm

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What is the name of this polymer (-C-C-)n

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poly(ethene)

What is an electrophile

a species that accepts a lone pair of electrons in a reaction

What is a carbocation

a hydrocarbon that contains a positively charged carbon atom, it is normally unstable and occurs as an intermediate in electrophilic additions

How are organic mechanism confirmed empirically

the products of the reaction are analysed when different anions are used in the reaction

What are structural isomers

hydrocarbons with the same molecular formula, but different structural formulae

What are stereoisomers

hydrocarbons with the same structural formula, but different arrangements of their atoms in 3D space

Why does stereoismerism occur around a double bond

free rotation is restricted around the double bond. when each carbon has two different groups attached to it different arrangements are possible about the C=C bond

What is cis-trans isomerism 

a type of E-Z isomerism that occurs when each carbon in the double bond has one group in common

what are some benefits of using fossil fuels

* fossil fuels are readily available due to all the infrastructure to use them already being in place
* fossil fuels are cheaper than alternatives
* fossil fuels are very efficient at producing energy: they have a high energy density

what are some risks of using fossil fuels

* burning fossil fuels causes greenhouse gases to be released which contribute greatly to global warming
* burning fossil fuels causes air pollutants to be released which pose a health risk to humans
* fossil fuels reserves are limited, and may start to run out in the near future

how is atom economy calculated

what are the benefits of a high atom economy

* less waste is produced from the reaction, which makes it cheaper
* the reaction requires less natural resources so it is more sustainable

What is electrolysis

the breaking down of a substance using electrical energy

How is electrolysis done in a lab

two non-reactive electrodes are connected to the power supply and placed in the solution, the power is turned on and electrolysis starts

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use the following setup

How does electrolysis work

* the cations are attracted to the cathode and are reduced
* the anions are attracted to the anode and oxidised
* the compound is therefore broken up as the two ions do not need each other to be stable

½ equations for electrolysis of NaCl

2Cl- (aq) ---→ Cl2 (g) + 2e-

2H+ (aq) + 2e- ----→ H2 (g)

What is an oxidising agent

a substance that removes electrons form other species by accepting electrons and getting reduced

What is a reducing agent

a substance that donates electrons to other species by getting oxidised

What does bromine look like under standard conditions

a red-brown liquid

What does iodine look like under standard conditions

a violet solid

Why does reactivity decrease down G7

* the number of electron shells increase, this increases the shielding from the nucleus as well as the atomic radius
* both of these factors decrease the nuclear attraction of outer electrons, making it harder for the halogen to gain electrons

Why does volatility decrease down G7

* halogens only have intermolecular london forces between their molecules
* as we move down the group the number of electrons in the halogen molecule increases, thus the london forces between the molecules become stronger, taking more energy to break

Why are halogens more soluble in cyclohexane than water

halogen molecules are non-polar, so they do not dissolve very well in polar solvents like water, but they will dissolve readily in non-polar solvents like cyclohexane

What are the solubilities of silver halide precipitates in ammonia

* AgCl: soluble in dilute ammonia
* AgBr: soluble only in concentrated ammonia
* AgI: insoluble in dilute and concentrated ammonia

How are hydrogen halides prepared

X- + H3PO4 ---→ HX + H2PO4-

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How are hydrogen halides prepared

how does HBr react with H2SO4

Why is HF a weaker acid than HCl

the F- ion forms ionic bonds with the H3O+ ions in solution, which means there is an equilibrium between the bound and unbound forms of the acid

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what are some uses of chlorine

* sterilisation of water
* bleaching for use in the paper or textiles industry

what are some risks associated with the storage and transport of chlorine

* chlorine is extremely toxic and can cause irreversible lung damage and eye damage upon exposure
* some chlorine compounds, such as those made when exposed to water, are carcinogenic