Chemistry Unit 3a (questions)

How was the periodic table arranged in the early 1800s?
they were arranged in order of atomic mass and when this was done a periodic pattern was noticed in the properties of the elements - hence the name 'Periodic Table'
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In 1864 how did Newlands arrange the Periodic Table?
Newlands' Law of Octaves (atomic mass): He noticed that every eighth element had similar properties and so he listed some of the known elements in groups of seven. But this pattern broke down in the third row with transition metals.
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Why was Newlands' work criticized?
1) his groups of elements did not have similar properties 2) he mixed up metals and non-metals 3) he did not leave any gaps for undiscovered elements
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How did Dmitiri Mendeleev order the Periodic table differently and in what year?
In 1869 hearranged the 50 known elements into a Table of Elements but he left gaps in order to keep elements with similar properties in the same vertical columns (known as groups). The gaps predicted the properties of the undiscovered elements.
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Later on, what evidence was there that Mendeleevs table may be correct?
As scientists discovered more elements they noticed that they fitted into the gaps that he left. also the realised that this was a good tool for predicting properties of elements.
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How is the modern Periodic Table arranged?
It is based on their electronic structure
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What is meant by 'sheilding'?
it is when inner shells of electrons "get in the way" of the nuclear charge, reducing the attraction.
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Why is an electron that has a higher energy level more likely to get lost?
As there is less attraction from the nucleus holding it in place - due to an increased distance from electron to nucleus and increased sheilding
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what are group one elements also known as?
The Alkali Metals
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What are the two main trends that can be seen as you go down group 1?
1) they become more reactive as the electron is further from the nucleus and so is easily lost 2) they have lower melting and boiling points
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How many outer electrons do alkali metals have?
one
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what type of compounds do alkali metals form and what colour compound do they form?
ionic compounds with non-metals to produce a white compound which dissolves in water to form a colourless solution
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what happens when alkali metals react with water?
they react very vigorously and produce hydrogen. they also form hydroxides that dissolve in water to give alkaline solutions
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what are the two main trends that can be seen as you go down group 7?
1) they become less reactive as it becomes harder to gain an electron as the outer shell is further from the nucleus 2)they get higher boiling and melting points
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what colours are the following halogens vapours: a)Fluorine b) Chlorine c) Bromine d) Iodine?
a) poisonous yellow gas b) poisonous dense green gas c) dense, poisonous red/brown volatile liquid d) dark gray crystalline solid or a purple vapour
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what type of bonds do Halogens form?
They form 1- bonds called halides when they (ionic) bond with metals
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What would happen if chlorine was mixed in an aquous solution of a bromine salt? and what would the equation be?
the chlorine would displace the bromine. Cl2 + 2KBr --> Br2 + 2KCl
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What are the properties of transition metals?
the typical properties of metals: 1) good conductors 2)very dense, strong and shiny 3) less reactive 4) they are much more denser, stronger and harder than group 1 metals and have much higher melting points (except mercury - liquid at room temp.)
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True or False: Transition metals often have more than one ion (isotopes)
True - the different ions usually form different coloured compounds.
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True or False: the compounds of transition metals are very colourful
True - the compounds are colourful due to the transition metal they contain. also the colours in gemstones and pottery glazes are due to transition metals
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True or False: Transition metals and their compounds all make bad catalysts
False: they all make good catalysts eg: iron is used in the habour process and nickel is used for turning oils into fats for making margarine
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What compounds cause hardness in water?
calcium and magnesium compounds: calcium hydrogen carbonate, magnesium hydrogen carbonate, magnesium sulfate, calcium sulfate
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how does the hardness of water affect how soap lathers?
hard water - lathers harder with soap & soft water - lathers easily with soap
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what is formed when hard water reacts with soap
scum (which is insoluble)
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what is formed when hard water is heated and why is this a problem?
scale is formed in pipes, boliers and kettles and is a problem as it reduces the efficiency as it acts a an insulator. it can also eventually block pipes
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how is temporary hard water formed?
carbon dioxide in the air dissolbes in rainwater to from carbonic acid. when this water trickles through rocks it reacts with the calcium carbonate from the rocks to from soluble calcium hydrogen carbonate
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a) name a chemical in soap b) what is formed when it reacts with hard water
a) sodium stearate b) calcium stearate (solid)
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how do you remove temporary hard water?
heating removes temporary hard water by decomposing to form solid calcium carbonate
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what is the word equation for removing temporary hard water?
calcium hydrogen carbonate (+heat) --> calcium carbonate + water + carbon dioxide
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how can hard water be softened?
it can be softened by adding sodium carbonate (washing soda). it reacts with the calcium compounds to form calcium carbonate and soluble sodium compounds and hardness is removed.
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how does an ion exchange work?
an ion exchange contains beads of ion exchange resin. they are insoluble and negatively charged and coated with sodium ions which have a +1 charge. hard water contains calcium and magnesium ions which contain a +2 charge
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ion exchange continued...
and as it flows through the exchanger they are attracted to the negative resin. calcium and magnesium ions have a greater positive charge so they displace sodium on the resin beads. sodium ions dissolve in water. eventually the beads need replacing
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what are the disadvantages of hard water?
1) more soap is needed (costs more money) 2) difficult to clean scum 3) damage kettles and heating systems 4) can be unsuitable for industrial processes eg. dying
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what are the advantages of hard water
calcium - builds stronger bones and teeth magnesium - effective metabolism
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what are the four steps that have to be taken to make sure our drinking water in safe?
1) the water passes through a mesh screen to remove big things 2) chemicals are added to make solids and microbes stick together & sink to the bottom 3) it is filtered through gravel beads to remove all solids 4) it is chlorinated to kill microbes
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what are the advantages of adding chlorine and fluorine to drinking water?
chlorine - helps to prevent diseases fluorine - helps reduce tooth decay
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what are the disadvantages of adding chlorine and fluorine to drinking water?
chlorine - could lead to an increase in certain cancers (can react with natural substances) Fluorine - in high doses can cause cancer and bone problems
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what is the definition of a reversible reaction?
a reversible reaction is one where the products of the reaction can themselves react to produce the origional reactants
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what is meant by an equilibrium?
the amounts of reactants and products will react a certain balance and stay there
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what is meant by a closed system?
none of the reactants or products can escape
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why is the overall affect in a reversible reaction nil?
the reactions cancel each other out as they are taking place at exactly the same rate in each direction
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True or False: you can move the 'position of the equilibrium' by altering the temperature and pressure
true
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True or False: all reactions are exothermic in one direction and endothermic in the other
true
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how does increasing temperature affect an equilibrium?
the endothermic reaction will increase to use up more heat
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how does decreasing temperature affect an equilibrium?
the exothermic reaction will increase to give out more heat
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True or False: in many reactions the volume is the same on both sides
false: many reactions have have a greater volume on one side
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how does raising the pressure affect an equilibrium?
it will encourage the reaction to produce less volume
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how does lowering the pressure affect an equilibrium?
it will encourage the reaction to produce more volume
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true or false: adding a catalyst changes the equilibrium position
false: catalysts speed up both the foreward and backward reactions the same ammound
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how does adding a catalyst affect an equilibrium?
it means the reaction reaches an equilibrium quicker but you end up with the same amount of product as you would without a catalyst
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what is the symbol equation for the haber process?
N2 + 3H2 --> 2NH3 (+ heat)
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what two elements are needed to make ammonia?
nitrogen and hydrogen
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what are the industrial conditions needed for the haber process? (pressure, temperature and catalyst)
Pressure: 200 atmospheres Temperature: 450 degrees Celsius Catalyst: iron
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why does the haber process have such a high pressure?
as it favours the forward reaction and so it provides a higher % yeild
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why does the haber process occur at a low temperature?
as the foreward reaction is exothermic and so a higher temperature would push the equilibrium in the wrong direction (away from ammonia - to the left)
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but a lower temperature means a slower rate of reaction?
450 degrees Celsius is a compromise between high yield but fast rate of reaction
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what function group do Alcohols have?
-OH
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what is the general formula for an alcohol?
Cn H2n+1 OH
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what are the first three alcohols in the homologous series and what are their formula?
Methanol (CH30H), Ethanol (C2H50H), Propanol (C2H7OH)
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what are the properties of alcohols?
1) they are flammable - they burn to produce carbon dioxide and water 2) the first three dissolve completely in water to form neutral solutions 3) they react with sodium to give hydrogen and alkoxides
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give an example of how ethanol is used as a solvent in the industry
it is the solvent in perfumes and aftershave lotions. it can mix with oils (gives the smell) and water (makes up the bulk)
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give an example of how ethanol when mixed with other chemicals can be used in the industry and what safety precautions have been made?
it forms 'Methylated Spriit' (or meths). and it is used to clean paint brushes and as a fuel. but it is dangerous so a purple/blue dye is added to stop people drinking it by mistake
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give examples of how alcohols are used as fuels and how this is an advantage
ethanol is used in spirit burners (it burns fairly cleanly and does not smell), it can be mixed with petrol to fuel cars (causes less pollution), some countries grow sugar cane which they ferment to form ethanol (renewable resource)
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what is the functional group of carboxylic acids?
-COOH
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what are the first three carboxylic acids called?
methanoic acid, ethanoic acid & propanoic acid
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what gas is produced when they react with carbonates?
carbon dioxide
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what does the salt's name end in with these reactions? and give and example
-anoate eg. methanoic acid will form a methanoate
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what will be produced when ethanoic acid reacts with sodium carbonate?
sodium ethanoate + carbon dioxide
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why are carboxylic acids weak acids?
they do not release many H+ ions which causes a solution to become acidic
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give two examples of carboxylic acids and their uses
ethanoic acid: when dissolved in water it makes vinegar - used for flavorings and preserving foods citric acid: used to make fizzy drinks and can remove limescale
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what is a general use for carboxylic acids?
when the have longer chains of carbon atoms they can be used to make soap and detergents
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what is the functional group of esters?
-COO-
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what are the reactants that need to be mixed to produce an ester and water?
alcohol + carboxylic acid
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what does their names end in?
-oate
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whta part of the name does the alcohol and acid form and give and example
the alcohol forms the first part of the name and the acid forms the second part: ETHanol + ETHANoic acid --> ETHyl ETHANoate + water
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why are esters ideal for perfumes?
they have pleasant smells and are volatile (easily evaporated)
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what is a disadvantage of their volatility?
it makes them highly flammable and therefore potentially dangerous
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staete one other property of an ester
they are not very soluable
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name three other uses of esters
1) used to make flavourings 2) they are used in ointments 3) other esters are used as solvents for paint, glue and in nail varnish remover
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name two more disadvantages of using esters
1) inhaling the fumes could irritate mucous membranes in the nose and mouth 2) some esters are toxic in high doeses so some people worry about health risks associated with synthetic food additives such as esters
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Other cards in this set

Card 2

Front

In 1864 how did Newlands arrange the Periodic Table?

Back

Newlands' Law of Octaves (atomic mass): He noticed that every eighth element had similar properties and so he listed some of the known elements in groups of seven. But this pattern broke down in the third row with transition metals.

Card 3

Front

Why was Newlands' work criticized?

Back

Preview of the front of card 3

Card 4

Front

How did Dmitiri Mendeleev order the Periodic table differently and in what year?

Back

Preview of the front of card 4

Card 5

Front

Later on, what evidence was there that Mendeleevs table may be correct?

Back

Preview of the front of card 5
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