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142 Cards in this Set

  • Front
  • Back

What is the general formula for Alkenes?

CnH2n

What sort of reactions do Alkenes usually go through in order to become Alkanes?

They open up or (polymerise) in Addition reactions

What would you call anything with this type of structure?

What would you call anything with this type of structure?

ARENES (or aromatic compounds)

How are we able to convert an Alkene into an Alkane using Hydrogen? Give an example:

Add Hydrogen gas to the Alkene along with a Nickel catalyst. An example of this is turning Ethene into Ethane at a temperature of 150 C



H2C=CH2+H2---------->CH3CH3

What does a double-bond in terms of sigma and pi look like?

Why are Alkenes more reactive than Alkanes?

Because Alkenes have a double bond, it will have quite a high electron density. Also, the pi bond protrudes the rest of the molecule therefore it is more likely that it will be attacked by electrophiles.

What are electrophiles? Give 2 examples:

Electrophiles are electron-pair acceptors (that are usually short of electrons and are therefore attracted to areas where there are many of them). There are 2 examples:



-Positively charged ions (H+, NO2+)


-Polar molecules (the slightly + is attracted to places with many electrons)

Identify the following hazard symbols (ignore the 3rd, 4th 6th, and 7th for Edexcel specification):

Identify the following hazard symbols (ignore the 3rd, 4th 6th, and 7th for Edexcel specification):

1.very toxic


2.explosive


5.highly flammable


8.harmful


9.irritant


10.dangerous for the environment

What is a hazard and what is a risk?

Hazard: anything that may cause harm.



Risk: the chance that what is being done may cause harm

What are risk assessments and how can risks be reduced?

Risk assessments assess the hazards of all the reactants, products, and procedures in an experiment and looks at how these risk can be reduced.


Risks can be reduced by:


-working on a smaller scale


-taking precautions (goggles, gloves)


-using chemicals with lower concentrations.

Describe the process of electrophilic addiction between a Bromine and an Ethene molecule and what it forms:

1) the double bond repels the Br2, polarising Br-Br.
2) the closer Br gives up the bonding electrons to the other Br and attaches to the C atom.
3)You get a positively charged carbocation intermediate. 
4) the Br- sticks to the C atom.

1) the double bond repels the Br2, polarising Br-Br.


2) the closer Br gives up the bonding electrons to the other Br and attaches to the C atom.


3)You get a positively charged carbocation intermediate.


4) the Br- sticks to the C atom.

Describe the process of electrophilic addition with Hydrogen Hallides (such as HBR) and what it forms:

1) H-Br is already a polar molecule. The +ve atom is attracted to the double bond electrons. 2)the H atoms gives up the bonding electrons to the Br and accepts an electron pair from the double bond. 3) The Br- sticks to the C forming: bromomethane.

1) H-Br is already a polar molecule. The +ve atom is attracted to the double bond electrons. 2)the H atoms gives up the bonding electrons to the Br and accepts an electron pair from the double bond. 3) The Br- sticks to the C forming: bromomethane.

What happens when hydrogen halides are added to unsymmetrical alkenes? Use hydrogen bromide with propene as an example?

2-bromopropane will be the major product because the secondary carbocation is attached to more alkyl groups making it more stable. There will be less 1-bromopropane because it is attached to less alkyl groups.

2-bromopropane will be the major product because the secondary carbocation is attached to more alkyl groups making it more stable. There will be less 1-bromopropane because it is attached to less alkyl groups.

What effects the stability of a carbocation?

the number of alkyl groups that it is attached to.



more alkyl groups = more stable


less alkyl groups = less stable

How would you test for Alkenes (carbon double bonds)?

Using:



Orange Bromine Water:


results: colourless solution (in presence of alkene)




Acidified Potassium Manganate:


results: also colourless

Describe what happens when Orange Bromine Water is used to test for Alkenes and why it occurs:

Bromine water is a dilute solution and it contains more water molecules than Bromine molecules so the carbocation is more likely to react with the H20 than the Br- therefore an OH group sticks to the C instead of another Br. This produces bromoalc...

Bromine water is a dilute solution and it contains more water molecules than Bromine molecules so the carbocation is more likely to react with the H20 than the Br- therefore an OH group sticks to the C instead of another Br. This produces bromoalcohol

Describe what happens when Alkenes are tested using Acidified Potassium Manganate (VII):

if you shake an alkene with acidified potassium manganate (vii), the purple solution decolourises because you've oxidised the alkene and made a idol  (an alcohol with 2 -OH groups)

if you shake an alkene with acidified potassium manganate (vii), the purple solution decolourises because you've oxidised the alkene and made a idol (an alcohol with 2 -OH groups)


Define "TRIGONAL PLANAR":

this means that the atoms attached to each other are formed at the corners of an imaginary equilateral triangle.

this means that the atoms attached to each other are formed at the corners of an imaginary equilateral triangle.


Which of the single or double bonds have the ability to rotate?

single bonds

What are stereoisomers and what are the 2 types?

have the same structural formula but a different arrangement in space.



the 2 types are:



- Z-isomers


- E-isomers

What causes alkenes to have stereoisomers?

restricted movement and lack of rotation of the double bonds.

what are alkenes with the same groups


diagonal from each other called?

E-isomers

trans-isomers

what are alkenes with the same groups on the same sides (horizontal) called?

Z-isomers

cis-isomers

What is the other name for a z-isomer?

cis


What is the other name for an E-isomer?

trans

Why can't we use the cis/trans naming mechanism instead of the Z/E?

we use Z or E when carbon atoms have completely different groups attached to them whereas we use cis or trans when the same exact groups are either or across or vertical to each other (it will also be more obvious).

What are polymers?

polymers are long chains of monomers


(small repetitive units)

Use ethene as an example of a monomer undergoing addition polymerisation and becoming _____________?

poly(ethene)
       not "ane"

poly(ethene)


not "ane"

How would you find out the monomer that was
used to form an addition polymer ( for example: polypropene)?

How would you find out the monomer that was


used to form an addition polymer ( for example: polypropene)?

you would find the repeating unit and change the single bond to a double bond; this will be your monomer used initially to form the addition polymer.

Are polymers reactive or unreactive? And how does their reactivity cause a problem?

they are not very reactive :/


this causes a problem because this means that they are not biodegradable therefore they are difficult to dispose of and causes environmental damage...

How can we minimise environmental damage by non-biodegradable polymers and use them for our own benefit?

-We can bury them in a landfill site after compacting them (we use this when they are difficult to separate from other waste, too


difficult to recycle)


- Recycle them (can be melted and remolded)


- Burn them. (heat can be used to generate electricity however, must be be monitored for toxic gases such as chlorine in PVC)

How can biodegradable polymers be made and how could we use them for our own benefit?

they can be made from starch and from the hydrocarbon isoprene. We can use them for plastic sheeting for plants to protect them from frost (polyethene).

What are some advantages and disadvantages of biodegradable polymers?

Advantages: - made from raw materials (therefore won't run out)


-when they biodegrade, CO2 is produced that can be used by plants in photosynthesis.


-save energy


Disadvantages:


- very expensive


-require specific conditions to biodegrade

Define each:
General Formula


Structural Formula


Empirical Formula


Molecular Formula


Displayed Formula


Skeletal Formula

General formula: an algebraic formula that can describe any member of a family of compoundsEmpirical formula: the simplest ratio of atoms of each element in a compoundMolecular formula: the actual number of atoms on each element in a molecule.Structural formula: shows the atoms carbon by carbon with the attached hydrogens and functional groups.Displayed formula: shows how every atom is arranged with lines to represent bonds between them Skeletal: shows carbon bonds ONLY and carbon and hydrogen atoms are not shown.

what is a homologous series?

a group of compounds with the same general formula.

what is the prefix/suffix for alkanes?

"ane"

what is the prefix/suffix for branched alkanes?

"alkyl" "-yl"

what is the prefix/suffix for alkenes?

"ene"

what is the prefix/suffix for halogenoalkanes?

chloro-/bromo-/ido-

what is the prefix/suffix for alcohols?

"-ol"

what is the general formula for alkanes?

Cnh2n+2

are alkanes saturated or unsaturated?

saturated

what is the general formula for cycloalkanes?

cnh2n


How do Halogens react with Alkanes?

they react to form halogenoalkanes when a hydrogen atom is substituted by chlorine or bromine in a photochemical reaction in a free-radical substitution reaction.

What is a photochemical reaction?

This is a reaction started by UV radiation

What are initiation reactions (show Chlorine)?

this is where free radicals are produced .
1) sunlight provides energy to break the Cl-Cl bond (photodissociation).
2) the bond splits equally and each atom keeps 1 electron and becomes a highly reactive free radical because it is unpaired.

this is where free radicals are produced .


1) sunlight provides energy to break the Cl-Cl bond (photodissociation).


2) the bond splits equally and each atom keeps 1 electron and becomes a highly reactive free radical because it is unpaired.



What are Propagation reactions ?

this is where free radicals are used up and created in a chain reaction.


1) Cl• attacks a methane molecule:


Cl•+CH4----->CH3•+HCl


2)the new methyl free radical CH3• can attack another Cl2 molecule:CH3•+ CL2---->CH3CL+Cl•


3)the new Cl• can attack another CH4 and so on until all the Cl2 or CH4 molecules are reacted with.

What are termination reactions?.

this is where free radicals join together to from a stable molecule.


Cl•+CH3•----->CH3Cl


CH3•+CH3----->C2H6

What is crude oil?

a mixture of hydrocarbons

Describe the process of Fractional Distillation of crude oil:

1)crude oil is vaporised at 350c


2)the vaporised crude oil goes up the trays. (the large hydrocarbons won't vaporise because their boiling points are too high therefore they will stay at the bottom as residue. 3)as the vapour goes up the fractioning column, it cools down and condenses at different temperatures.


(bubble caps prevent them from spilling back).They are then drawn off at different levels of the column.


4)those with very low boiling points (at the top) will be drawn off as gas.

What can the following products of fractional distillation be used for:


-mineral oil


-diesel


-kerosene


-napatha


-residue


-petrol

mineral oil: lubricating


diesel:heating fuel


kerosene:jet fuel, heating


napatha:processed to make petrochemicals


petrol: gas for cars


residue: Fuel oil, Bitumen (for roads), Wax (candles)

Define Cracking

this is the process in which heavy hydrocarbons or long-chain alkanes and alkenes are broken to form smaller hydrocarbons.

Name two types of Cracking, how they take place, and what they produce:

Thermal cracking: takes place at temperatures up to 1000C and pressures up to 70 atm. It produces lots of alkenes.



Catalytic cracking: takes place at about 450C with very little pressure and uses a zeolite catalyst. It produces aromatic hydrocarbons and motor fuels.

Why would we try and reform straight-chain alkanes in petrol into branched-chain alkanes, cycloalkanes and aromatic hydrocarbons? Give an example of reforming a straight-chained alkane such as hexane.

branched-chain, cycloalkanes and aromatic compound allow the fuel to burn more efficiently.

branched-chain, cycloalkanes and aromatic compound allow the fuel to burn more efficiently.

Name 3 harmful emissions that fossil fuels produce when burnt and what are their effects on the environment:

-Sulfur Oxides: Dissolves in the moisture in the air creating sulfuric acid which acidifies lakes and rivers and kills aquatic life.


-Carbon Monoxide (incomplete combustion): cause health problems due to restriction of oxygen.


-Nitrogen Oxides: also affects acid rain. And causes breathing problems.

How do greenhouse gases relate to global warming?

The Earth absorbs radiation from the sun and remits it as infra-red radiation. The greenhouse gases absorb this radiation and re-emit some of this to Earth.

State the types of melting points, its typical state (solid/liquid/gas), whether it conducts electricity when solid and liquid, and whether it is soluble in water for the following:


-Ionic bonding


-simple molecular (covalent)


-Giant molecular (covalent)


-Metallic

Ionic: high melting point, solid state, does not conduct electricity when solid (but does when liquid), it is soluble in water.


Simple molecular covalent: low melting point, usually liquid or gas with the exception of Iodine, does not conduct electricity at ALL, sometimes soluble (depending on its polarity) Giant molecular (covalent): high melting point, solid state, does not conduct when solid (except graphite), not soluble in water. Metallic: high melting point, solid state, conducts electricity, not soluble in water.

Why is it easier to boil simple covalent compounds in comparison with metallic or ionic compounds?

you only need to overcome their weak intermolecular forces (London forces) that hold the molecules together. These are much weaker than ionic, covalent, or metallic bonds therefore their melting/boiling points are much lower.

How is Silicon Dioxide structured and what shape does it form?

-they form a giant covalent structure (like diamond) between the silicon and oxygen atoms.
-Each silicon atom is bonded to 4 oxygen atoms in a tetrahedral arrangement to form a big crystal lattice.

-they form a giant covalent structure (like diamond) between the silicon and oxygen atoms.


-Each silicon atom is bonded to 4 oxygen atoms in a tetrahedral arrangement to form a big crystal lattice.

Describe metallic bonding:

this is when the outermost electrons of a metal atom are delocalised and are free to move about the metal and leaves positive metal ion.these positive ions are attracted to the deloca-lised negative electrons to form a lattice of closely packed positive ions in a sea of delocalised electrons.

What affects the strength of a metal's conductivity and melting point?

-the # of delocalised electrons per atom affects the melting point (the more of them, the higher it will be).


-the size of the metal ion affects the melting point because it affects the charge density (higher charge density, higher melting point)


-more delocalised eletrons, better conductivity.

What is Dative Covalent Bonding?

a covalent bond (a shared pair of electrons) in which both electrons come from the same atom.

a covalent bond (a shared pair of electrons) in which both electrons come from the same atom.


What can use as evidence for covalent bonding?

Electron  Density Maps.

Electron Density Maps.

What are the two types of bonds that covalent bonds can be?

Sigma and Pi bonds

How is a sigma bond formed?

How is a sigma bond formed?

when two s orbitals overlap, they make a sigma bond giving the highest possible electron density between the 2 nuclei.

when two s orbitals overlap, they make a sigma bond giving the highest possible electron density between the 2 nuclei.

How is a pi bond formed?

How is a pi bond formed?

when two electrons in p orbitals overlap, they make a pi bond.

when two electrons in p orbitals overlap, they make a pi bond.

Are pi or sigma bonds more reactive? Why?

pi bonds are weaker than sigma bonds because pi bonds are less tightly bound to the two nuclei than the sigma bond. This means that the pi bonds are more reactive than sigma bonds.

Why are large anions polarized more easily than small anions?

their electrons are further away from the nucleus therefore electrons on large anions can be pulled away more easily towards cations.

How are partially covalent bonds formed?

This occurs when a small cation with a large charge (that is very polarising) attracts electrons towards it from the anion and gives a compound partially covalent character.

This occurs when a small cation with a large charge (that is very polarising) attracts electrons towards it from the anion and gives a compound partially covalent character.

Why is it that sometimes, the theoretical lattice energy is not very close to the experimental lattice energy of ionic lattices?

some ionic compounds have covalent character which causes the theoretical lattice energy and experimental lattice energy to differ unlike purely ionic lattices.

What do Born-Haber cycles show and what are they used for?

they show enthalpy changes when a solid ionic compound is formed from its elements in their standard states. They show 2 routes (the indirect and the direct). They are used to calculate lattice energies (the energy change when gaseous ions form 1 mol of an ionic solid under standard conditions).

What are the steps of a Born-Haber cycle?

1)enthalpy of atomization.


2)enthalpy of atomization of next element


3) 1st Ionisation energy


4)electron affinity


5)lattice energy


6)standard enthalpy of formation

What is meant by standard conditions?

298K, 100kPa

What 2 ways could we prove the existence of ions? Describe the procedure.

The migration of ions on wet filter paper:


electrolyse a green solution of copper(II)chromate(VI) the filter paper turns blue at cathode and yellow at anode because the solution is initially green as it contains both blue and yellow ions. When an electrical current is passed through it, they separate as the negative ions move to the anode, and the positive to the cathode.


Electron density maps: shows that there are spaces between the ions where the density of the electrons is zero - no shared electrons.

Why is it that the ionic radius of a metallic element smaller than it's atomic radius?

because metals lose electrons when they form ions, the positive charge on the nucleus is larger than the negative charge in the electron cloud therefore the electrons are pulled closer.


-also, positive ions have their outer shells emptied therefore, electrons are closer to the nucleus and there is less shielding.

Whys is it that the ionic radius of a non-metal is larger than the atomic radius?

Non-metals will gain electrons when they form ions therefore there is greater negative charge in the electron cloud than there is positive so there is greater repulsion between electrons making it expand.

What happens to the ionic radius as you go down a group?

it increases (because the atomic number is also increasing)

What are Isoelectronic ions?

these are ions of different atoms with the same number of electrons but different number of protons.

What happens to the ionic radius of a set of isoelectronic ions (same number of electrons, different # of protons) as the atomic number increases?

the atomic radius decreases because the electrons are attracted more and more pulling them closer to the nucleus (since the # of protons is increasing but the #of electrons remains the same).

What are Ionic Crystals?

they are giant lattices of ions.

What are the chemical formulas and charges for the following:


-Nitrate


-Carbonate


-Sulfate


-Ammonium

-Nitrate (NO3 -)


-Carbonate (CO3 2-)


-Sulfate (SO4 2-)


-Ammonium (NH4 +)

What are positive ions called?

Cations

What are negative ions called?

Anions

Define Homolytic fission

This is when a bond splits equally and each atom gets to keep one electron forming two uncharged radicals.

Define Heterolytic fission

This is when the bond splits unevenly and both electrons move to one atom which forms two different species (a cation and anion).

What is a mass spectrometer used for?


it can be used to calculate the relative atomic mass, relative molecular mass, relative isotopic abundance and molecular structure

Describe the 5 steps that a sample would go through in a Mass Spectrometer:

1) vaporisation (sample turned into gas)


2)Ionisation (gas particles are bombarded with high energy electrons leaving behind positively charged ions).


3) Acceleration: the positive ions are accelerated using an electrical field.


4) Deflection: the ions' paths are altered by the magnetic field based on their mass therefore lighter ions are deflected more.


5)Detection: a mass spectrum is produced.

How would you calculate the relative isotopic abundance from a Mass Spectrum?

-multiply the %relative isotopic abundance with the relative isotopic mass for each.


-add these values together


-divide by 100 (only if percentages were used)

Label a Mass Spectrometer:

What is Carbon Dating and how is it used?

it is a method for working out the age of carbon-based objects using the carbon-14 model. We do this by using its half life to understand how old something is.

Give two examples of real-life application for Mass Spectrometry:

-pharmaceutical industry: uses mass spectrometry to identify compounds in possible drugs through urine samples.



-Probes to Mars: used mass spectrometry to study the composition of Mars.


Name the sub-shells in order of increasing energy, its # of orbitals and the maximum # of electrons it can hold:

Order: s, p, d, f



#of orbitals: 1 3 5 7



Max # electrons: 2 6 10 14

How are s-orbitals shaped?

they are spherical

they are spherical

How are p-orbitals shaped?

they are dumbbell shaped

they are dumbbell shaped

Name the sub-shells in order of increasing energy:

True or False:



the number of outer electrons only decides the chemical properties of an element and not its number of neutrons.

TRUE

Which two metals donate their 4s electrons to the 3d sub-shell first instead of filling the 4s first?

Chromium and Copper

Where are the s-block elements located?

Groups 1 and 2


(as well as Helium and Hydrogen (1s))

Where are the p-block elements located?

Groups 3,4,5,6,0


(excluding Helium)


Where are the d-block elements located?

the transition metals from Scandium to Zinc.

Define first ionisation energy

the energy required to remove one mole of electrons from one mole of gaseous atoms.



eg: Na(g) → Na+(g) + e-


What are 3 factors that would affect ionisation energy?

-Nuclear charge: the more protons there are, the more positively charged the nucleus is and the more attraction there will be between its electrons and nucleus.


-Distance from nucleus: attraction decreases the greater the distance is.


-Shielding: the more the electrons are, the greater the distance between the valence electrons and the nucleus will be decreasing the size of attraction.

Define Shielding

When the number of electrons between the outer electron and the nucleus increase, the outer electrons feel less attraction towards the nucleus; this is due to shielding.

What are two trends in first ionisation energies?

1) as you go down a group, first ionisation energies decrease.



2)the first ionisation energies increase as you move across a period.

Define Second Ionisation energy

The second ionisation energy is the energy required to from 1 mole of di-positive gaseous ion from 1 mole of positive gaseous ions.



e.g: O+(g)----> O2+ + e-

What happens to the successive energies as you get closer to the nucleus?

they increase


(since there is less repulsion and they are held more strongly by the nucleus)

What are the rows called in a periodic table?

periods

What are the columns called in a periodic table?

groups

what do all elements within the same period have in common?

the same # of electron shells

what do all elements within the same column have in common?

the same # of outer-shell electrons.

What does the group number tell you?

how many electrons are present in the outer-shell.

Label a periodic table according to the s, p and d groups:

What happens to the Atomic Radius as you move across a period?

it decreases


(the proton # increases so the positive charge increases in the nucleus so electrons are pulled in closer to the nucleus making the atomic radius smaller.)

What happens to the shielding as you move across a period?

it remains constant (the same)

What happens to the ionisation energies as you move across a period?

they increase


(because the # of protons is increasing which means there will be stronger nuclear attraction)

Why is there a drop in the ionisation energies between groups 2 and 3 ? use the example below:



Eg: Be 1s22s2 1st ionisation energy = 900 kJ mol



B 1s22s22p1 1st ionisation energy=799 kJ mol

This occurs because the the 2p sub-shell has a slightly higher energy than the 2s sub-shell. This means that Boron's valence electron is a little further away from the nucleus. This distance will mean that there will not be as much attraction between the nucleus and outer electron so the 2s2 electrons give the 2p sub-shell some partial shielding resulting in a lower ionisation energy.

Why is there a drop in the ionisation energies between groups 5 and 6? use the example below:



Eg: N 1s22s22p3 1st ionisation energy =1400kJ mol



O 1s22s22p4 1st ionisation energy=1310kJ mol

the outer electrons are both in the same sub-shell therefore there will be no difference in shielding. However, because the Oxygen's valence shell has 2 pairs while the Nitrogen only has one pair, there will be more repulsion in the Oxygen's valence electron pairs which make it even easier to remove. If you compare it with Nitrogen's pair (along with a single unpaired electron) you will see that Nitrogen will have a higher ionisation energy because it it harder to remove an unpaired electron than a paired electron.

Why do the melting points of these metals (Li, Be, Na, Mg, Al) start to increase across a period?

this occurs because the metal-metal bonds get stronger because the metal ions have an increasing number of delocalised electrons and a decreasing radius which leads to higher charge density which attracts the ions more strongly.

Why do the noble gases usually have the lowest boiling and melting points?

they are usually monatomic (individual atoms) resulting in very weak London forces.

Define Enthalpy Change:

it is the heat energy transferred in a reaction at constant pressure and is measured in kJ mol-1

Do Exothermic reactions release or take in energy and is their enthalpy change negative or positive? What about Endothermic reactions?

Exothermic: They give OUT energy. Their enthalpy change is negative



Endothermic: They take IN energy. Their enthalpy is positive.

Define activation energy:

the minimum amount of energy required to begin breaking reactant bonds.

Define Standard Enthalpy of reaction.

the enthalpy change when the reaction occurs in the molar quantities shown in the chemical equation under standard conditions in their standard states.

Define Standard Enthalpy of Formation

the enthalpy change when 1 mole of a compound is formed from their standard states under standard conditions.

Define Standard Enthalpy of Combustion

the enthalpy change when 1 mole of a substance completely burns in oxygen under standard conditions.

Define Standard Enthalpy of Neutralisation:

the enthalpy change when 1 mole of water is formed from the neutralization of hydrogen ions under standard conditions

Define Standard Enthalpy Change of Atomisation:

the enthalpy change when 1 mole of an element in its standard state is converted to gaseous atoms.

What formula is used to calculate enthalpy change when we use calorimetry?

q=mcΔt



enthalpy change = mass of water x specific heat capacity of water (4.18 J g-1 K-1) x the change in temperature of the water.



(water may be substituted for other solutions but the heat capacity may be different)

How would you carry out calorimetry for a flammable liquid?

1.Measure 100cm3 of water in the measuring cylinder.


Pour the water into the steel can and record its temperature. 2. Choose a spirit burner.Record the name of the fuel, and the mass of the whole burner (including the lid and fuel inside). 3. Clamp the steel can, and set it up so that the spirit burner will fit comfortably under it. 4.Light the wick of the spirit burner, and put it under the steel can. 5. Stir the water gently with the thermometer, and watch the temperature. When it has increased by 20°C, put the flame out. Record the new mass of the whole burner

What are some experimental errors with both general and flammable-liquid calorimetry?

general calorimetry:


-most of the heat may be absorbed by the container rather than the water.


-heat is always lost to the surroundings depending on how well you insulate the container.



flammable-liquid calorimetry:


-combustion may be incomplete - less energy given out.


-some flammable liquid may evaporate and escape

What is calorimetry used for?

it is used to find how much energy is given out by a reaction by measuring the temperature change of something.

it is used to find how much energy is given out by a reaction by measuring the temperature change of something.

What is the difference between accuracy and reliability?

accuracy means how close to the true value your results are.



reliability means how reproducible your results are.

What does Hess' law state?

the total enthalpy change is independent of the route taken.

Define Bond Dissociation Enthalpy (or just bond enthalpy):

the amount of energy required to break bonds in 1 mole of a gaseous compound.

Define mean bond enthalpy:

the energy needed to break one mole of bonds in the gas phase, averaged over many different compounds.

Define the Scientific Process:

This is when scientists ask questions, suggest answers and finally, test them to see if they are correct.

What are the four steps of the scientific process:

1)ASK a question


2)SUGGEST an answer


3)MAKE a prediction


4)CARRY OUT tests

How would you produce hydrated ammonium iron (II) sulfate from iron, ammonia and sulfuric acid?

1) add a know mass of iron fillings to an excess of warm sulfuric acid and stir until reacted to form iron (II) sulfate solution.


2)Add a little ammonia to react completely with the iron.


3)Leave the solution to evaporate until blue green crystals form.


4)Collect the crystals by filtering then wash them with water.


5)dry crystals between two pieces of filter paper.

Define Atom Economy:

it is the measure of the proportion of reactant atoms that become part of the desired product in the balanced chemical equation.

What formula is used to calculate the % atom economy?

% atom economy = (molecular mass of desired


product ÷ sum of molecular masses of all products) x 100

Which has higher atom economy:



-Addition reactions


-Substitution reactions

Addition reactions


(they have 100% atom economy)

What is the formula for calculating percentage yield?

(Actual yield ÷ theoretical yield) x 100%