Random Stuff Double Flashcards
Chemical equation for decomposition of hydrogen peroxide
2H2O2 —> 2H2O + O2
Explain why water has much lower melting point than sodium oxide
Attractions between water molecules (covalent bonds) are much weaker so easily overcome with little energy. Whereas the attraction between sodium and oxide ions is a lot stronger as ionic bonds are stronger and need lots more energy for bonds to break.
The electronic configuration of a sodium atom is 2.8.1
Sodium oxide, Na2O, is an ionic compound formed when sodium reacts with oxygen.
Describe, in terms of electrons, what happens when sodium oxide is formed in this reaction
Electron transfer
Sodium loses, oxygen gains
Sodium loses 1 electron and oxygen needs to gain 2 electrons
define activation energy
minimum amout of energy reqiured by colliding particles to react
define isomerism
compounds with same molecular, different structural
4 characteristics of same homologous series
- trend in physical
- similar chemical
- same general formula
- each group differs by CH2
conditions for cracking
600-700 degrees
alumina or silica catalyst
define cracking
thermal decomposition method to convert longer chain molecules into shorter more useful short chain alkanes or alkenes to meet supply and demand
define ionic bonding
strong electrostatic force of attraction between oppositely charged ions
which bonding is shown through dot and cross diagrams
covalent, electrons need to add up to 8, can be from multiple of same elements to add up
order of crude oils from 40degrees to 400 degrees
- refinery gas
- gasoline
- kerosene
- diesel
- fuel oil
- bitumen
does refinery gas or bitumen have a high viscosity and high boiling point
bitumen
what happens as you go down from refinery gas to bitumen
- boiling point increase
- viscosity increases, darker colour
- longer molecules - higher boiling point to break
process used to separate crude oils
fractional distillation
explain why crude oil containing sulfur or oxides of nitrogen as an impurity is a problem when using crude oil fractions as fuels
**when sulfur is burned, it forms sulfur dioxide and it can mix with rain to form acid rain. **acid rain makes land infertile, corrodes limestone buildings and destroys wildlife and ecosystems.
Uses of :
Refinery gas
Gasoline
Kerosene
Diesel
Fuel Oil
Bitumen
- domestic heating and cooking
- fuel for cars
- fuel for domestic heating, fuel for aircraft
- fuel for buses and train engines, trucks
- fuel for ships and industrial heating
- used to pave roads
cations
ammonium
hydrogen
silver
lead
zinc
- NH4 +
- H +
- Ag +
- Pb 2+
- Zn 2+
anions
Hydroxide
Nitrate
carbonate
sulfate
- OH -
- No3 -
- CO3 2-
- SO4 2-
Does diamond conduct electricity
Giant Covalent Structure
* No charged species that are free to move
so the substance won’t conduct electricity
Does graphite conduct electricity
Giant Covalent
Electrons are present between the layers of carbon atoms (electricity is a flow of electrons) and these delocalised electrons can move and carry a current.
Graphite will conduct electricity.
Does Fullerene C60 conduct electricity
Simple molecular Structure
* No charged species that are free to move so the substance won’t conduct electricity
Does diamond have a high boiling point?
Giant covalent structure.
* Many strong covalent bonds (Electrostatic force of attraction between the shared pair of electrons and the nuclei of the atoms involved).
* Each carbon atoms is bonded to 4 other carbon atoms (tetrahedral arrangement)
* These bonds require lots of energy to break.
* Therefore these substances have very high melting points.
Does graphite have a high boiling point?
Giant covalent structure.
* Many strong covalent bonds
* Each carbon atoms is bonded to 3 other carbon atoms. One electron from each atom is delocalised(not involved in bonding)- this leads to electrical conductivity (see below)
* These require lots of energy to break.
* Therefore these substances have very high melting points.
Does fullerene C60 have a high boiling point?
NO
(larger) simple molecular structure.
* Weak intermolecular forces of attraction between the molecules.
* These require little energy to overcome them (break)
* Therefore these substances have low melting points, but higher than other smaller molecules.
As the size of molecules increases, there are more/stronger intermolecular forces and the melting/boiling points increase.
State why diamond is hard, but graphite is soft
diamond –> tetrahedral structure, 3D structure with each carbon bonded to 4 other carbons, so fixed lattice position
graphite –> has layers that can slide over each other
Diffusion of ammonia and hydrogen chloride
What is the white ring of solid ?
ammonium chloride
explain why ammonium chloride forms closer to hydrogen chloride than ammonia solution
ammonia diffuses faster
white ring forms after 5 minutes, explain why it takes so long even though gas particles move very fast
air particles in tube, so gas particles hit air particles, so diffusion is slower
give chemical equation for complete combustion of pentane (should be fully balanced)
C5H12 + 8 O2 –> 5 CO2 + 6 H2O
why is carbon monoxide dangerous
reduces blood’s capacity to carry oxygen around body
describe how crude oil is separated into fractions
- crude oil is pre heated and vapourised
- vapour fed into fractionating column, hotter at bottom, cooler at top
- vapour rises, cools and condenses at different heights
- different fractions have different boiling point ranges
define molecule
fixed number of atoms joined together by covalent bonds
what is empirical formulae, molecular formulae, general formulae, structural formulae and displayed formulae
empirical = smallest ratio
molecular =number of stuff there
general = general formula for homologous series
displayed = how it is drawn
structural = how it is set out
how to work out empirical formulae
1.find mass
2. find Ar or Mr
3. find moles (moles = mass/Mr)
4. divide by smallest number, round number to nearest 1/2 number and then times by 2 if needed
define saturated and unsaturated
saturated = compound containing single bonds only
unsaturated = compound containing one or more double (or multiple) bonds
define ion
charged particle
2 properties of metal wire used in flame test
high melting point, unreactive
why is platinum wire sometimes used in flame test
high melting point, is unreactive and doesn’t produce a colour in a flame itself
state why wire should be clean when used in flame test
to get rid of impurities that could affect reliability of the results or give a false positive
describe noble gas properties
why do they have low melting/boiling points
properties = monoatmoic, colourless gas
full outer shells = This electronic configuration is extremely stable so these elements are unreactive and are inert
what do the period and group signify on periodic table
period = number of shells
group = number of electrons in outer shell
define atom, element, compound and mixture
atom = smallest part of an element which still behaves as that element
element = substance made up of only one type of atom
compound = substance made up of more than one type of atom chemically bonded together
mixture = Different types of particles in the same physical space but not chemically joined
what is the anion and cation
anion = negatively charged ion
cation = positively charged ion
colours formed in flame test for cations:
Li+
Na+
K+
Ca2+
Cu2+
Li+ is red
Na+ is yellow
K+ is lilac
Ca2+ is orange-red
Cu2+ is blue-green
describe a flame test
Dissolve the unknown solid in water
2. Soak a splint in the solution
3. Put the splint into the non-luminous flame of the Bunsen burner
4. Observe the colour of the flame
Non- luminous flame as orange can affect results
Describe a chemical test for ammonium ions
- Add sodium hydroxide solution (NaOH(aq)) and warm.
- Put damp red litmus paper in the mouth of the test tube
- As ammonia gas (NH3(g)) is produced and it is an alkaline gas the damp red litmus paper turns blue.
Describe a test for Cu2+, Fe2+ and Fe3+
- Add sodium hydroxide solution (NaOH(aq)) and a precipitate is produced
Cu2+ = copper( II) hydroxide forms which is a blue precipitate
Fe2+ = iron(II) hydroxide forms which is a green
precipitate . . If left it forms a brown precipitate (iron(III) hydroxide) around the top of the solution.
Fe3+ = iron(III) hydroxide forms which is a brown
precipitate
Describe test for halide ions –> Cl-, Br-, I-
1.Add dilute nitric acid (HNO3(aq)) to make it acidic.
2. Add silver nitrate solution (AgNO3(aq)) and a precipitate is observed.
Cl- = Silver chloride forms which is a white precipitate
Br- = silver bromide forms which is a cream precipitate
I- = silver iodide forms which is a yellow precipitate
Why is dilute nitric acid added?
to remove any carbonates and / or hydroxides that may form precipitates and interfere with the results
Describe a test for carbonates (CO3 2-)
1.Add dilute nitric acid (HNO3(aq)) and carbon dioxide (CO2(g)) is produced (effervescence is observed).
2.You can test for carbon dioxide by bubbling the gas through limewater which goes cloudy (milky).
Describe a test for sulfates (SO4 2-)
- Add dilute nitric acid (HNO3(aq)) to make it acidic.
2.Add barium chloride solution (BaCl2(aq)) and a white precipitate of barium sulfate (BaSO4(s)) is observed.
test for hydrogen H2
Add a lit splint to the mouth of the container that contains the gas to be tested and if it produces a squeaky pop it is hydrogen
test for oxygen O2
Add a glowing splint to the mouth of the container that contains the gas to be tested and if the splint relights it is oxygen
test for carbon dioxide CO2
Bubble the gas through limewater and if the limewater goes cloudy (milky) it is carbon dioxide
test for ammonia NH3
Add a damp strip of red litmus paper to the mouth of the container that contains the gas and if the litmus paper turns blue it is ammonia
test for chlorine Cl2
Add a damp strip of (red or blue) litmus paper to the mouth of the container that contains the gas, if the litmus paper is bleached white it is chlorine
describe a test for the presence of water using anhydrous copper(II) sulfate
Addthe substance to (white) anhydrous copper(II) sulfate and if the substance is water, then the white solid will turn blue to form hydrated copper(II) sulfate CuSO4 + 5 H2O ⇌ CuSO4.5H2O(s)
What happens if you heat blue hydrated copper(II) sulfate strongly?
the solid turns white to form
anhydrous copper(II) sulfate This is a reversible reaction. Reversible reactions can take
place in both directions
problems caused by disposal of addition polymers
- toxic greenhouse gases produced -> global warming
- landfill sites getting full
dot and cross diagram for nitrogen (N2)
2 circles of N
6 electrons in middle
2 on outside on each side
explain why C60 fullerene has a much lower melting point than graphite
- graphite is giant covalent
- lots of energy required to melt graphite and break bonds
- C60 is simple molecular
- weak intermolecular forces of attraction overcome easily
- more energy required to break strong covalent bonds in graphite than weak intermolecular forces in C60
can a mixture melt over a range of temperatures
yes
a pure substance has a ____ melting and boiling point
fixed
percentages of 4 most abundant gases in air
21 % = oxygen O2
78.1 % = nitrogen N2
0.9% = argon Ar
0.04 % = carbon dioxide CO2
define corrsoion
chemical reaction between a metal and oxygen in the air
define redox reaction
reaction in which both reduction and oxidation are happening
define rusting
chemical reaction between iron and oxygen and water from the air in which rust (hydrated iron(III) oxide) is formed
Gas :
arrangement, movement and energy of particles
Arrangement: Particles are far apart and there are no forces between them.
Movement: Particles are free to move.
Energy: Particles have more kinetic energy than liquids and solids.
Liquid :
arrangement, movement and energy of particles
Arrangement: Particles are close together but irregular.
Movement: Particles are free to move.
Energy: Particles have less kinetic energy than gasses but more than solids.
Solid :
arrangement, movement and energy of particles
Arrangement: Particles are close together and regularly packed.
Movement: Particles vibrate around a fixed point.
Energy: Particles have less kinetic energy than both liquids and gasses
gas to solid
solid to gas
sublimation
solid -> liquid
liquid -> gas
gas-> liquid
liquid-> solid
melting
evaporating
condensing
freezing
when sodium oxide is heated, it reacts to form sodium metal and sodium peroxide, Na2O2
Complete equation
2 Na2O –> Na2O2 + 2Na
physical test for pure water
test the boiling or freezing point
100 degrees or 0 degrees
define rate of reaction
A measure of change in concentration of a reactant (or product) with time. The greater the change in concentration over a particular time the faster the rate of the reaction
define catalyst
substance that speeds up a chemical reaction but which is chemically unchanged at the end of the reaction
how does a catalyst work
A Catalyst works by providing an alternative pathway with lower activation energy
describe Properties of Simple Molecular Substances
boiling point high or low?
conducts electricity?
Simple molecular structure.
* Weak intermolecular forces of attraction between the molecules.
* These require little energy to overcome them (break)
* Therefore these substances have low melting points.
- Simple molecular structure
- there are no charged species that are free to move so the substance will not conduct electricity
describe Properties of Giant Ionic structures:
boiling point high or low?
conducts electricity?
Giant ionic structure (ionic bonds)
Strong ionic bonds (strong electrostatic forces of attraction between oppositely charged ions) are broken
The strong bonds require lots of energy to break them.
Giant ionic structure (ionic bonds)
The ions are free to move when the ionic compound is molten/in solution, but not in solid form when the ions are fixed in position and cannot move.
Explain why sodium oxide does not conduct electricity
(sodium oxide is ionic (because compound of metal and non-metal)
Particles are in a fixed position, so no free moving electrons that can carry current
oppositely charged ions - extra electrons in outer shells gained or lost to form full outer shell - so no free moving electrons
4 factors affecting rate of reaction
- surface area of reactant
- concentration of reactant
- temperature
- adding a catalyst
Why does increasing the surface area of a solid reactant increase the rate of a reaction?
More particles of the solid are exposed on the surface so there are more successful collisions per unit time.
what does concentration of a solution tell us?
how much solute is dissolved in a given volume of solvent
Why does increasing the concentration of a solution of increase the rate of reaction?
Why does increasing the pressure of a gas increase the rate of a reaction?
- There are more particles per unit volume so more successful collisions per unit time.
- There are more particles per unit volume (allow particles are closer together) so more successful collisions per unit time.
Why does increasing the temperature increase the rate of a reaction?
Particles move faster so there are more successful collisions per unit time. Particles also have more energy so more of those collisions (more collisions per unit time) have energy greater than the activation energy.
Explain why adding a catalyst increases the rate of a reaction.
A catalyst provides an alternative reaction route of lower activation energy so more collisions (or particles) have energy greater than the activation energy.
3 methods to prevent iron rusting
- barrier methods
- galvanising
- sacrificial protection
how rusting is prevented by barrier methods
Rusting may be prevented by stopping the water and oxygen getting to the iron with a barrier of grease, oil, paint or plastic.
how rusting is prevented by galvanising (coating in zinc) - alloying - only iron can rust
(coating in zinc) also prevents water and oxygen getting to the iron, but with galvanising even if the barrier is broken the more reactive zinc corrodes before the less reactive iron. During the process, the zinc loses electrons to form zinc ions.
how rusting is prevented by sacrificial protection
Oxygen reacts with other metal first
incomplete combustion equation (balanced)
octane + oxygen –> carbon + carbon monoxide + water
how does simple distillation work
Simple distillation is used to separate a solvent from a solution. It is useful for producing water from salt solution.
Simple distillation works because the dissolved solute has a much higher boiling point than the solvent. When the solution is heated, solvent vapour evaporates from the solution. The gas moves away and is cooled and condensed. The remaining solution becomes more concentrated in solute as the amount of solvent in it decreases.
what happens when bromine water reacts with an alkene
colourless product formed
bromine water goes from orange to colourless
name of reaction to test for alkenes and the condition needed
addition reaction
needs to occur in dark
give the balanced chemical equation for the reaction of ethene and bromine water
C2H4 + Br2 –> C2H4Br2
(gets rid of alkene double bond)
give name of product formed
1, 2 Dibromoethane
give the balanced chemical equation for the reaction of but-2-ene and bromine water
C4H6 + Br2 –> C4H6Br2
give name of product formed
1, 2 Dibrobutane
what happens if bromine reacts with an alkane?condition?
orange -> brown
substitution reaction
UV light
give the balanced chemical equation for the reaction of methane with bromine in the presence of UV light
CH4 + Br2 —————> CH3Br + HBr
UV light
give the name of product(s) formed
bromoethane + hydrogen bromide
alkane reacts with bromine, alkene reacts with ____________
bromine water
give the name of product(s) formed
bromoethane + hydrogen bromide
give the balanced chemical equation for the reaction of methane with bromine in the presence of UV light
C3H8 + Br2 —————> C3H7Br + HBr
UV light
give name of product(s) formed
1 bromoproane + hydrogen bromide
equation for rust
iron + oxygen –> hydrated iron (II) oxide
what has been oxidised in equation
iron -gained oxygen, lost electrons
half equation for iron (III) ions involved
Fe –> Fe3+ + 3e-
define addition polymerisation
The process of joining many small monomers to form one long polymer chain
define monomer and polymer
monomer - small molecule that joins together with many other small molecules to form one large polymer
polymer - large molecule formed by the joining many small monomers together
sacrificial protection
iron is a better _______ reagent than magnesium
iron gains ________ more ______ than magnesium
Fe3+ + 3e- –> _____
Mg –> _________
iron is _________
magnesium is _______
iron is _________ ________ MAGNESIUM
oxidising
electrons, easily
Fe
Mg2+ + 2e-
oxidised
reduced
reduced, before (magnesium rusts before iron, so iron doesn’t rust straight away)
rate of reaction =
Units(g/min)
1000/time period OR amount of reactant used or amount of product formed/time
An investigation of the reaction between marble chips and hydrochloric acid:
calcium carbonate + hydrochloric acid –> calcium chloride + water + carbon dioxide
Give balanced equation
CaCO3 (s) + 2HCl (aq) –> CaCl2 (aq) + H2O(l) + CO2(g)
how does practical work
Marble chips, calcium carbonate (CaCO3) react with hydrochloric acid (HCl) to produce carbon dioxide gas. Calcium chloride solution is also formed.
Using the apparatus shown the change in mass of carbon dioxide can be measure with time.
As the marble chips react with the acid, carbon dioxide is given off.
what is the purpose of the cotton wall at top of conical flask
to allow carbon dioxide to escape, but to stop any acid from spraying out.
describe graph showing this reaction
- at start, graph is very steep showing lots of carbon dioxide produced per minute - reaction is fast
- middle, graph getting less steep, - reaction is showing down
- graph becomes horizontal showing that no more carbon dioxide is being reduced - reaction has stopped
example of dilution of coloured solutions
i) dilution of coloured solutions
Dissolving potassium manganate(VII) in water demonstrates that the diffusion in liquids is very slow because there are only small gaps between the liquid particles into which other particles diffuse.
The random motion of particles cause the purple colour to eventually be evenly spread out throughout the water.
Adding more water to the solution causes the potassium manganate(VII) particles to spread out further apart therefore the solutions becomes less purple. This is called dilution.
Practical: determine the approximate percentage by volume of oxygen in air using a metal or a non-metal
The following 3 experiments can be used to determine that oxygen (O2) makes up approximately 20% by volume of air.
COPPER
The copper is in excess and uses up the oxygen to form copper oxide (CuO).
All the oxygen in the air is therefore used up, and so the volume of the air decreases by about 20% (the percentage of oxygen in air).
Practical: determine the approximate percentage by volume of oxygen in air using a metal or a non-metal
The following 3 experiments can be used to determine that oxygen (O2) makes up approximately 20% by volume of air.
IRON
Iron wool in tube is slightly damp
Invert the tube in beaker of water, so tube mouth is covered
Measure the length of column of air
Leave for 1-2 weeks
Use difference/initial x 100 to calculate oxygen in air
The iron reacts with the oxygen in the air (rusting). Mass of iron increases
As long as the iron, oxygen and water are all in excess, the total volume of air enclosed by the apparatus decreases by about a fifth (20%) over several days.
IRON + OXYGEN + WATER –> HYDRATED IRON(III) OXIDE
Practical: determine the approximate percentage by volume of oxygen in air using a metal or a non-metal
The following 3 experiments can be used to determine that oxygen (O2) makes up approximately 20% by volume of air.
PHOSPHORUS
The phosphorus is lit with a hot wire.
It reacts with the oxygen in the air and causes the water level in the bell jar to rise by about 20%.
alkanes are best fuel because
easily ignited
use of alkenes
to maek polymer - starter material to produce other chemicals
why is carbon dioxide bad
contributes to global warming as is greenhouse gas
describe the formation of carbon dioxide from the thermal decomposition of metal carbonates, including copper(II) carbonate
On heating metal carbonates thermal decompose into metal oxides and carbon dioxide
Observation: green powder (CuCO3) changes to a black powder (CuO)
CuCO3 –> CuO + CO2
Why is taj mahal changed in appearance after years, as it is made of calcium carbonate and sulfur dioxide is present in the atmosphere
Sulfur dioxide into water
Causes acid rain
Erodes limestone as it reacts away the limescale
How to know if it is a catalyst
Measure mass before and after, if same , it is catalyst
what type of structure/ bonding does carbon dioxide have?
Simple molecular structure
Covalent bonds
Properties of co2
Colourless odourless
More dense than air
Fairly soluble in water and used in fizzy drinks, used in fire extinguishers as it displaces oxygen which is needed for fire
Why is helium better for balloons than hydrogen
Less dense than air
Hydrogen is explosive air
3 ways to produce carbon dioxide
Burning hydrocarbons
Thermal decomposition of carbonates
Hydrochloric acid + calcium carbonate —> calcium chloride + water + carbon dioxide
What type of reaction is rusting?
Oxidation
What does fractional distillation separate
Miscible liquids at different boiling points
How is oxides of nitrogen formed in car engines
Reacts with oxygen then ignited by spark
classify elements as metals by using their electrical conductivity and the acid-base character of oxides
Basic oxides (Alkaline) - react to form salt and water
Good conductors of electricity
High melting and boiling point
Malleable
classify elements as non-metals by using their electrical conductivity and the acid-base character of oxides
Acidic oxides (Acidic/neutral)
does not conduct electricity (except for graphite)
Low melting and boiling point
Flaky
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