chemisty C3

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  • Created by: Izzy
  • Created on: 18-05-13 21:06
In what order did Mendeleev place the atoms? And why did he leave gaps?
In atomic weight, because some elements hadn't been discovered yet.
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How do we now arrange elements?
In atomic number order, with similar properties
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Why do atoms in the same group have similar properties?
Because they have the same about of electrons in their outer shell
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As you go down the group...
...the number of electron shells increases and the atoms get bigger
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What happens to larger electrons? And why?
They lose electrons more easily, and gain them less easily. Because the electrons in the outer shell are further away and have a weaker force to the nucleus.
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What happens to reactivity in group 1? and why?
It increases as you go down the group, SINGLE electron in outer shell is easier to lose
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What happens to reactivity in group 2? and why?
It decreases down the group, an extra electron is less easily attracted into the shell
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Why are alkali metals stored in oil?
Because they are highly reactive with the air
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Give three properties of the alkali metals
Low density, soft, shiny
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Where are the transition metals?
In the middle of the periodic table
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Give 4 physical properties of the transition elements
Good conductors of electricity and energy, hard and strong, high density, high melting points
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Give a chemical property of the transition elements
not very reactive - useful for structural material and catalysts
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What is the difference between Fe2+ and Fe3+
Fe2+ = green, Fe3+ = reddish-brown
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Four properties of the halogens?
Poisonous, coloured vapour, Low melting and boiling points, poor conductors of energy and electricity
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What type of bonding do the halogens have?
covalent and ionic
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What do all halogens form?
ions with a single negative charge in their ionic compounds
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How does a displacement reaction take place between halogens?
The more reactive halogen can displace the less reactive halogen in a solution of one of its salts.
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What is the difference between hard and soft water?
Soft water forms a rich, thick lather. Hard water contains dissolved compounds that react with soap to form scum
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What is dissolved in hard water?
Dissolved calcium and magnesium ions (from rocks in rivers)
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What does hard water produce when heated?
Scale
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Benefits of hard water?
Develops teeth and bones, prevents heart disease
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What is temporary hard water?
Water thats hardness is removed by boiling
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What is permanent hard water
When the calcium and magnesium ions from salts are not removed when heated.
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Explain the washing soda method of softening hard water
the sodium carbonate reacts to precipitate out the magnesium and chlorine ions
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Explain the ion exchange column
the column is packed with a resin of sodium ions, the hard water passes through the column, and the sodium ions are exchanged for the magnesium and calcium ions
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What happens in a water filter?
the carbon in the filter reduces levels of chlorine and pesticides, the ion exchange removes calcium, magnesium, copper and lead ions, silver particles discourage the growth of bacteria
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How is pure water made?
By boiling water and condensing the steam, we don't use it for drinking water because it would be expensive
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give some pros and cons of fluoride in water?
Pros: nobody has been affected so far, reduce cavities in teeth, protects from heart disease (from tooth decay), and only tiny amount. Cons: Fluorosis, ethically wrong, should get to chose, you cant set a safe limit
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What is used to compare the amount of energy released by different fuels?
Calorimeter
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what is the equation for working out how much energy is released?
energy = mass of water x specific heat capacity x rise in temperature
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how would you work out the energy released per mole?
You would times the energy released by (the formula mass over the amount of fuel burned(g))
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What is the difference between exothermic and endothermic?
Endothermic is bond breaking (energy supplied), exothermic is bond making (energy lost)
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How do you calculate energy released using bond energies
Add up all the bonds in the formulas then calculate the difference
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What is the alternative fuel being developed? and why?
Hydrogen because it burns well and produces no pollutants
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What are the dangers of hydrogen?
could be explosive, cant store it, also supplying it would use electrolysis which would release co2 into the air
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Explain the hydrogen fuel cell
Where the cells are fed with hydrogen and oxygen to produce water which produces a constant electrical current, producing energy
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What colour do the following ions go in a flame test? Lithium, sodium, potassium, calcium and barium
Crimson, yellow, lilac, red, green
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What ions for white precipitate when added to sodium hydroxide and how can you tell the difference?
Aluminium, calcium and magnesium. If more solution added, aluminium dissolves, the other two do not.
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Describe the positive ion test for copper, iron2 and iron3?
copper blue precipitate, fe2 green precipitate, fe3 reddish-brown precipitate
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How do we test for negative ions in a carbonate?
React with dilute acid, test product gas with limewater to see if it goes cloudy
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How do we test for the halides (chloride, bromide and iodide?)
First add dilute nitric acid, then silver nitrate solution, white precipitate = chloride, cream = bromide, yellow = iodide
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How do we test for sulfates?
add dilute hydrochloric acid, then barium chloride if there is a white precipitate, barium sulfate is present
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why do we add nitric acid and hydrochloric acid before ion tests?
to get rid of any carbonate ions
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What is titration
Used to measure how much acid and alkali needed to neutralise each other
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What is the end point of a reaction?
When an acid-alkali reaction is finished
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How to find 1 mole of a substance?
Add up atomic masses and add (g)/dmHow
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Titration: How do you work out the mass of a substance in the solution?
Add up atomic mass in 1000cm2 and divide accordingly
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What do forensic scientists analyse?
Drugs, paints, fire debris, fibres, gunshot residues, medicine (forensics)
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Whats the difference between qualitative testing and quantative testing?
Qualitive - which ions are present, Quantative - how many
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What would chemical equilibrium mean?
When the rate of the forward reaction is the same as the backward reaction
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What happens when the concentration is lowered in a reverse reaction?
The rate of the forward reaction decreases
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What does increasing/decreasing the pressure do to a reversible reaction?
Increasing = favours less molecules of gas, decreasing = favours more molecules of gas
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What does increasing and decreasing the temperature do to a reversible reaction?
Increasing favours endothermic reaction, decreasing favours exothermic reaction
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What is ammonia used for?
fertiliser
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What are the raw materials used to make ammonia?
Nitrogen from air, hydrogen (from natural gas methane)
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Describe the haber process
Nitrogen and hydrogen purified, passed over iron catalyst at high temperatures and pressures --> ammonia
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Why is ammonia not produced at higher pressures if its more effective?
Too expensive to keep such high pressures
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Why is the temperature not very low to produce ammonia when the yield is higher?
Because it slows down the rate of reaction
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What are the functional groups for alcohol, carboxhylic acids and esthers
-OH, -COOH, -COO-
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What are alcohols used for?
solvents, fuels, alcoholic drinks.
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How do alcohols reacts when burnt, and with sodium
burn with a clear blue flame and give off carbon dioxide and water, reacts with sodium, fizzes = hydrogen
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What is produced when ethanol is oxidised?
Ethanoic acid
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Why are carboxhylic acids called 'weak acid'
not all the molecules ionise in water
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How is an ester made?
Reacting a carboxhylic acid with and alcohol with an acid catalyst
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What is the pain property of esters?
Very volatile - evaporate very easily
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What are the dangers of alcohol?
Health problems, days lost at work, antisocial behaivour
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Card 2

Front

How do we now arrange elements?

Back

In atomic number order, with similar properties

Card 3

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Why do atoms in the same group have similar properties?

Back

Preview of the front of card 3

Card 4

Front

As you go down the group...

Back

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Card 5

Front

What happens to larger electrons? And why?

Back

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