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Y11 chemistry CC10/11 Electrolysis Equilibrium

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  • What is the last state in the life cycle assessment of a product
    manufacture and packaging of product
    obtaining and processing raw materials
    disposing of the product
    using the product
  • State why copper can be produced by heating copper oxide with carbon
    carbon is more reactive than copper, and will displace copper from copper oxide
  • What is meant by the degree of dissociation?
    It is the extent to which an electrolyte breaks up into ions
  • Identify the Cations: Ca2+, SO3, NO3-, Br-, Fe3+, NO2,
    Ca2+ and Fe3+
  • What are the products: Zn(s) + H2SO4(aq) -->
    H2(g) + ZnSO4(aq)
  • What happens at the highlighted point?
    equilibrium (when it levels off)
  • What is the half reaction that occurs at the cathode for Al2O3
    Al3+ + 3e- --> Al(s)
  • Define electrode
    rod of metal/graphite which carries current in/out solution
    chemical decomposition produced by passing electric current
    a negatively charged particle
    a positively charged metal
  • What is the balanced Haber equilibrium equation? (include states of matter also)
    N2(g) + 3H2(g) <--> 2 NH3(g)
  • Why is bioleaching slow?
    the bacteria take time to decompose the ore
  • Which of the following is TRUE about this process? N2(g) + 3H2(g) <--> 2NH3(g)
    This is not an equilibrium reaction
    When nitrogen is added more hydrogen is produced
    This is the Haber process
    When ammonia is added, more nitrogen is produced
  • What would be the product at the cathode from the electrolysis of molten sodium chloride?
    sodium
  • What is the source of hydrogen in the Haber process?
    natural gas or water or steam
  • This happes when a metal reacts with oxygen, making the metal weaker over time
    corrosion
  • Name the electrode that diminishes during electroplating.
    Anode
  • Why are articles electroplated? [two reasons]
    To prevent corrosion and to make them attractive
  • State the charge of the electrode where oxidation takes place.
    Positive
  • Explain how OH- ion yields oxygen gas at the anode.
    4 OH- ons lose an electron each and give 2 molecules of water and one molecule of oxygen
  • Which of the following does not describe oxidation?
    gain of oxygen
    loss of hydrogen ions
    loss of electrons
    gain of electrons
  • What is: a state of balance between continuing processes.
    dynamic equilibrium
  • Explain why ionic solids cannot be electrolysed
    ions cannot move around in a solid (when electrolysis occurs ions need to move to electrodes)
  • When a compound is oxidised, what happens in terms of oxygen?
    oxygen is gained
  • State the entire electro-chemical series of metals in proper order.
    K, Ca, Na, Mg, Al, Zn, Fe, Pb, [H], Cu, Hg, Ag
  • What is electroplating?
    Electroplating is the electrolytic process of deposition of a superior metal on the surface of a baser metal or article.
  • Predict products: magnesium + copper sulfate -->
    copper + magnesium sulfate
  • What would be the product at the anode from the electrolysis of molten sodium chloride?
    anode: chlorine
  • State the order of reactivity of the three metals, giving a reason for your answer.
    increasing reactivity: Z, X, Y - X displaces Z so X is more reactive than Z; X does not display Y so Y is more reactive than X
  • When calcium carbonate is heated it decomposes to form calcium oxide and carbon dioxide. Which of the following is NOT true about this reaction?
    Equation: CaCO3(s) <--> CO2(g) + CaO(s)
    carbon dioxide gas is released
    The equilibrium can be shifted if calcium oxide is removed
    equilibrium cannot be achieved as this is an open system.
  • Which is the negative electrode? Which ions migrate to it?
    Cathode, Cation
  • a naturally occurring solid material from which a metal or valuable mineral can be extracted profitably. What is this?
    ore
  • In the copper sulfate electrolysis practical, why was a variable resistor required?
    the current can vary in the experiment but a variable resistor keeps it constant
  • What type of ion is Fe2+
    cation
  • What type of ion is F-?
    anion
  • When a sodium chloride solution is electrolysed, why is hydrogen produced instead of sodium metal?
    hydrogen ions are discharged more readily than sodium ions
  • What catalyst was used in the Haber process to produce ammonia from nitrogen and hydrogen?
    enzymes
    iron
    sunlight
    iodine
  • Why is pure water a non-electrolyte?
    Because contains only molecules and not ions to conduct electricity
  • In the copper sulfate electrolysis practical, what was the gas that was produced?
    oxygen
    nitrogen
    carbon dioxide
    hydrogen
  • What is the half reaction that occurs at the anode for Al2O3
    2O2- --> O2 + 4e-
  • How does equilibrium shift if nitrogen dioxide is added to this reaction? (justify your answer)
    shift to products (right) to compensate for the stress on reactants
  • What happens to the amount of products when a reaction reaches equilibrium?
    it stays the same
  • What is bioleaching?
    extract metals in ores using microorganisms to oxidize metal
    use bacteria to convert copper into gold
    using enzymes to do metal plating
    use bacteria to shine metals
  • Zinc oxide reacts with carbon to form zinc and carbon dioxide in a redox reaction. Explain which substance has been oxidised and which has been reduced.
    oxidised: carbon (gained O/lost e-); reduced: zinc oxide (lost O/ gained e-)
  • What is: a state of balance between continuing processes.
    dynamic equilibrium
  • Taking waste metal and changing it into a useful item. What process is this?
    recycling metal
  • Which ions would be attracted to an anode: Ca2+, SO3, NO3-, Br-, Fe3+, NO2,
    NO3- and Br-
  • How does equilibrium shift if nitrogen dioxide is removed from this reaction? (justify your answer)
    shift to reactants (left) to compensate for the lack of stress on reactants
  • How does equilibrium shift if heat is added to this reaction? (justify your answer)
    shift to reactants (left) because it is exothermic the heat is a product and adding more stress to products shifts to reactants
  • What are the products: Mg(s) + H2O(aq) -->
    H2(g) + MgO(s)
  • electrolysis can only occur in
    solids
    gases
    any of the other choices
    solutions or liquids
  • What happens to an equlibrium of gases when you decrease gas pressure
    in direction that uses up the substance that has been added
    direction that forms less gas molecules (decreases pressure)
    direction that forms more gas molecules (increases pressure)
    direction that forms more of the substance removed
  • In the copper sulfate electrolysis practical, why did you have to clean the copper electrodes?
    so that the copper deposited will adhere to the electrode ( because when it is oxidized, the copper metal is not on the outside)
  • What is the ratio of hydrogen: oxygen gas volume when acidified water is oxidized
    2:! hydroge: oxygen because the formula for H2O is 2 hydrogen for every 1 oxygen
  • Plants absorb mineral ions through their roots. What is this?
    phytoextraction or phytomining
  • What is the source of nitrogen in the Haber process?
    air
  • Which half reaction of molten lead shows oxidation?
    the anode
  • Metals which ionize most readily are at the ________ of the series. [top / bottom]
    top
  • Predict products: copper + magnesium sulfate -->
    no reaction (because copper is lower on reactivity series and not reactive)
  • Which metal can only be extracted from its ore by electrolysis
    gold
    zinc
    sodium
    lead
  • In the following reaction: 2H2O(g) <--> 2H2(g) + O2(g) If you increase the pressure, what will happen?
    The equilibrium will shift to reactants (left) because there are fewer gas molecules on the left.
  • Mention any two conditions for electroplating [with reasons]
    To be discussed
  • In the copper sulfate practical, why did we use propanone to wipe the electrodes before they were weighed?
    to dry them, so that the weight represents only the copper and not the water.
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