Exam Questions Flashcards
Name the type of bond between the hydrongen and the chlorine atoms in a molecule of hydrogen choride
Covalent bond
Suggest two causes of experimental error in an experiment
change in temerature loss of gas reacted unexpectadly using balance incorrectly faulty balance
Why is it important to repeat the experiment?
To find a mean
What is the meaning of the term of a precipitation reaction?
Insoluble substances beiong formed
How can magnesium hydroxide be seperated from the calcium chloride solution?
Filtration
Name a method that can be used to change calcium chloride solution into solid calcium chloride
Crystallisation
half equation:
Ca —> Ca ^2+ + ….
2e^-
Why can the formation of calcium ions from calcium atoms be described as oxidisation?
Because electrons are lost
Explain why diamonds are hard
Because they have a giant structure, covalent bonds which are very strong
How is ammonia separated from unreacted nitrogen andhydrogenn in the separator
Mixing is cooled so that ammonia turns into a liquide
Why does the yield of ammonia at equilibrium increase as the temperature is decreased?
Becuase it is an exothemic reaction
Explain, in terms of particles, why increasing the temperature makes a reaction fo faster
particles move faster
collide more frequently
Why does the yield of ammonia at equilibrium increase as the pressure is increased?
Greater volume on left hand side than on the right
Why would a higher pressure not be used?
Coast
Give two reasons why it does not matter that the percentage of yield ammonia is low.
Unreacted gases are recycled
Rate if production is fast
Describe the structure and bonding of gold
Giant structure
Delocalised electrons
Possitive ions and negative electrons attract to each other
Why is gold a good conductor of electrisity?
free electrons
The surface of some metals, such as iron, corrode when exposed to the air. Suggest why this reduces the electrical conductivity of the metal
ionic compound formed
ions not free to move
How did Wohler prove that a life force is NOT needed to make organic compounds?
He made another organic comound
In 1828 most scientists continued to beleieve that a life force was needed to produce an organic compound. Suggest by they did not believe Wohler’s idea until 1845.
lack of evidence before
later there was more evidence
How solid lead nitraste can be obtained fro lead nitrate solution?
evapouration
The water and CO2 produced escape from the test tube, why?
because they are gases
Suggest two reasons why al of the points do not lie on the line of best fit
results not recoreded correctly
apparatus error
How could a graph give a conclusion?
by having a straight line
Why does the rate of reaction increase whent he conetration increases?
increase in the frequency of collision
particlies are closer together
Why do metals have a high melting point?
gaint structure
made of positive ions surrounded by free elecrons
stonge bonds
so alot pf energy is needed to break them
What does the term “nano” tell you about the carbon nanotubes?
they are very small
Why do carbon nanotubes conduct electricity?
free electrons
one non-bonded electron from each atom
Mg^2+ I^-
What happens when magnesium reacts with iodine?
magnesium loses 2 electrons
iodine gains 1 electron
Explain why a high temperature is needed to melt potassium iodide
bonds are strong
because oppositly charged ions attract
giant structure
HOw does a decrease in temperature affect the yeild of ammonia at equilibrium?
increase yeild
becuase the reaction is exothermic
HOw does an increase in pressure affect the yield of ammonia at equilibrium?
increase yield
becuase greater volume on the left than on the right
Do the reactants need to be heated?
yes to strat the reaction
A student investigates the reaction between magnesium and hydrochloric acid. Give two observatios the student could make during the reaction.
effervescence
magnesium dissolves
Name the type of reaction between aqueous ammonia solution and an acid
neutralisation
Davy first tried to elecrolise a solid potassium salt to produce potassium. Explain why this electrolysis did NOT work
current cannot flow because ions couldn’t move
The sudent exoected to see potassuim metal at the negative elcrode, but instead saw bubbles of a gas.
name the gass produced at the negative elecrode
explain why this fas was produced and why pottassium was not produced
gas = hydorgen
the ions as positve
potassium is more reactive than hydrogen
potassium metal was produced at the negative electrode. Describe how potassium atoms are formed from potassium ions
loses one electron
Why are alloys harder than pure metals?
because particles in alloys are different sizes, so the layers are distroted and they can no longer slide over one another
describe the stucture of a dimonde
giant structure
stong bonds between atoms
convalent bonds
each carbon atom froms 4 bonds
describe the structure and bonding in a thermosftening polymer and explain why thermosoftening polymers melt when heated
large molecules with weak intermolecular forces and are easily btocken when heated
Explain why, in terms of structure, CO2 is a gas, even at a low tempwerature
has simple molecules. The intermolecular forces are qweak and only a small amount of energy is needed to overcome the forces
What is the purpose of chromatography?
To split the properties of the gases
What information do the molecular ion peak from the mass spectrometer give about the substances?
relative molecular mass
suggests why scientists in 1800 could not extract aluminium from alumina
no method
How was Wohler able to prove that he had made a new metal?
when tesated it had the properties of a a metal
properties were dofferect from other known matals
Give two reasons why they should have repeated the experiment
improve reliablitly
reduce the effect of errors
name the method that could be used to seperate magenisium hydroxide from the solution
filtration
Why is the reaction a reduction reaction?
because electrons are gained
Why are metals very good conductors?
because their electrons can move freely through the structure and carry a charge
Suggests one reason why nanosized particles of silver might help to transfer heat bettwe than normal sized particles
more can fit into the gaps
Why does an increase in preassure increase the yield of ethanol at equilibrium?
2 particles on the left and one the right
Ethanol has a low boiling point and evapourates easily, why?
becaus ethe bonds betweent the molecules are weak
Why is graphene strong?
giant structuer
convalent bonds
which are strong
Why can graphene conducet electricity?
free electrons
3 electrons per atom used in bonding
suggests why a sheet of graphite which has a large number of carbon layers would not be suitable for the touchscreen
because it is opaque
In peper chromatography the start line line should be drawn with a ruler and a …….
Why?
pencil
the pencil will not run whereas the ink would
Why do differenct compounds seperate a gas chromatograpohy colum?
pass through the colum at different speeds adna different retnetion times
Why is chlorine a gas at room temperature?
simple molecule convalent bonds between the atoms weaf forces betweenthe molecules weak intermolecular forces therefore low boiling point and is a gas ar room temperature
Why is sodium chloride a solid at room temperature?
ionic bonds electrostatic attractions giant lattice strong bonds large amounts of engery needed to break the bonds so it is a solid
State the effects of increasing the pressure on the rate of reaction
increases the rate of reaction
more particles in a smaller space
increase frequency of collision
What is actovation energy?
The minimum amount of energy particles need for a reaction to take place
A student concluded that potassium would NOT be a suitable metal to react with sulfuric acid, why?
too reactive
would be dangerous
What happens at the negative electrode (with zinc chloride)?
zinc ions are attracted to the negative electrode
gains 2 electrons
froms zinc
Whta is an indication that a reaction is done at a high temperature?
gas is produced
endothermic:
A reaction wich takes in energy from its surroundins
Suggests one reason why carbon nanotubes are used in lubricants
nanotubes can slide over each other
There are weak intermolecular forces / no convalent bonds between them
Mg^2+ O^2-
What happens when magnesium atoms react with oxygen atoms to produce magnesium oxide?
Mg loses 2 electrons
O gains 2 electrons
They get a full outer shell
suggests why gas melts at a lower tmeperature than silicon dioxide
weaker bonds
Explain, in terms of ions, why sodium chloride solution conducts wlwctricity
ions can move
2 5 7 13
which of these pH values could be the one of sodium hydroxide?
13
suggests how the student could check the reliablitlity of the results
repeat the experiment
Explai in terms od electrons how an ion atom (Fe) can change into an iron(III) ion (Fe^3+)
it loses
3 electrons
Explain why metals can be shaped
made pf layers
which can slide over one another
What would you observe when magnesum reacts with an acid?
hydrogen gas is produced
it get hot
HOw could you obtain solid magnesium sulfate from this solution?
crystalisation
Why are catalysits used in chemical reactions?
they speed up a reactio
Suggests why different catalysists are used for different experiment
different temperatures
Suggests and explain why the use of nanosized particles reduce the cost of the catalyst converter
smaller than normal sized atoms
bigger surface area
less catalys needed
Describe the structure and bonding in silicon dioxide and explain why it is a suitable material for making welding blakets
giant structure
strong bonds
high melting point
Why is using methanol an advantage to the artists?
less drying time
describe the bonds in methanol
stong convalent bonds
Explain why methanol has a low boiling point
bonds between the molecules are weak
Explain why the best equilibrium yields is obtained when the pressure is high
fewer product molecules
suggest one reason why the yields obtained is less than the maxiumum yield
reversable reaction
suggests why silver stops unpleasent smell when wearing socks with silver nanoparticles in them
kils bateria
The silver nanoparticles are more effective at preventing unpleasent smells than normal sized silver particles, why?
react faster
Name the particles which carry the electric current through:
the metal wire
the solution
The metal wire = electrons
The solution = ions
Hydrogen has a low melting point, why?
weak intermolecular forces
Name the raw materials that are used to supply nitogen and hydrogen
Nitrogen = air Hydrogen = natural gas
Explain why a temperature of 405 0C is used than a much higher temperature por a much lower temperature
higher temperature gives a low yield because reaction is exothermic
but at low temperature the rate is too slow
Ammonia is made by passing nitogen and hydrogen over hot iron.
Why is iron used in the reactor
How is ammonia separated from the unreacted nitogen over hot iron?
1) catalyst
2) cooled
What property of diamond makes it suitable for use on the cutting end of a drill bit?
hard
Why is diamond hard?
giant stucture
convalent bonds
bonds are stong
ecach carbon forms 4 bonds
Explain why graphite is a good conductor of electricity and why diamond is not
graphit:
free eletcrons
one electron from each atoms is delocalised and is free to move around the structure
diamond:
all electrons are used in bonding
suggest why sodium oxide and potassium oxide are dangerous in contact with the skin
corrosive
explain why changing the pressure does not affect the yield of hydrogen at equilibrium
same number of moecules on both sides of the euation
Suggest why the best yields of hydrogen at equilibrium is obtained at low temperature
forward reaction is exothermic
Scientists have developed catalysis which allow the reaction to take place quickly at lower temperature. How could this be good for the manufacture and for the environment?
more product
less fuel needed
How is the nucleus of an oxygen-18 atom different from the one of an oxygen-16 atom?
O-18 has 2 more neutrons
If a reaction is exothermic, how will the temperature of the mixture change as the glue is mixed and a chemical reaction takes place?
increases
Why so substances with giant covalent structures have a high melting point?
nods are strong
a lot of energy is needed to break the bonds
Suggest why using “nanocoated” tennis balls would be good for the environment
less tennis balls need to be made
less pollution caused
Explain why the gel containing ions in solution can cunduct electricity
because the ions are free to move and carry a charge
Suggest how the use of a catalyst might reduce costs in the industrial production of aspirin
use a lower temperature
Explain why the highest equilibrium yield of methanol is obtained at high pressure
fewer product molecules than reactant molecules
Why are some local people worried about the use of chlorine compounds?
poisons released into the environment
Simple molecules like water have low boiling point, why?
weak intermolecular forces
Explain why at equilibrium the yield of ammonia for the reaction is greater at low temperatures
gives out heat/ exothermic reaction
What type of substance would be added to the water to provided the OH^- inons?
an alkali
what is a precipitate?
it is an insoluble substance
what method could be used to seperate the precipitate from the solution?
filtration
structure and bonding of graphite
only weak forces between the layers layers can slide over each other delocalised electrons electrons can carry a charge giant structure
What are the features of a reation which allows hydrogen to be released?
it is reversible
Why is hydrogen stored in a fuel tank filled with lithium nitride would be safer in an accident than a cylinder full of hydrogen?
hydrogen has bonded with lithium nitrate and therefore it does not leak
Explain how a flurine atom can hange into a fluoride ion, F^-
an electron is gained
Explain why the electrode would dry faster when washed with propanone instead of water
propane evapourates faster
Describe how electrolises is used to make pure copper from a lump of impure copper
copper loses electrons
copper forms at the positive ions
copper sulfate solution
impurities collected at the bottum
Why is silica used to make bricks for high-temperature furnaces
high melting point
covalent bonds
all atoms joined together no free electrons
What is ment by electrolyse?
electric current is passed through an ionic compound
Discus the economic, safety and environmental factors to be considered when there is an ammonia factory
Economic-factory provides employment
Safety-escape of dangerous chemicals
Environment-CO2 is produces by the burning fuels
What could cause a solution to go cloudy?
Sulphur which is insoluble
How can gas chromatography separate substance in a mixture of compounds?
Substances carried by gas
Through a tube at different speeds
Suggests how an experiment could be improved
Use a more accurate digital thermometer
Put a lid on
Insulate the beaker
Give one reason why coins are not made of pure copper
Not including cost
Malleable
Softer
Aluminium is manufactures by the electrolysis of molten mixture of cryolite and …
Aluminium oxide
The relative atomic mass of an element compares the mass of an atom of an element with the mass of an atoms of …
Carbon-12
If it is a solid you…
Filter
If it is a solution you …
Evaporate
Give some ethnic reasons why a compound if iodine should NOT be added to sodium chloride as food
Right to chose
Different amounts neededNo evidence for the result
