Chemistry paper 1

• The negative ions are called cations which moves to the negative electrode called the cathode
• Negative non-metal ions are oxidised (loose electrons) to form the element at the anode (positive electrode)
• At the cathode (negative electrode) if H+ ions and metal ions are present hydrogen will be produced, if the positive metal ions form an element that is more reactive thathant hydrogen. If the positive metal ions form an element that is less reactive than hydrogen the pure metal will form around the cathode
• The only elements that are less reactive than hydrogen is Gold silver platinum and copper
• At the anode ( positive electrode) if OH- and halide ions are present the molecules of elements in group 7 will form (chlorine bromine iodine) if there are no halide ions present then the OH- ions are discharged and oxygen will form
• Explain why the reactivity of elements change as you go down group 1 (4)

  . reactivity increases as you go down the group

  . because the outer electron is further away from the nucleus

  . so there is less attraction between the nucleus and the outer electron

  . the atom looses the electron easier
• Explain why sodium oxide has a high melting point (3)

  . sodium oxide is a giant ionic lattice

  . with strong electrostatic forces of attraction between oppositely charged ions

  . so large amounts of energy is needed to break the bonds
• Explain why alloys are harder than pure metals (3)


  . in an alloy the atoms are of different sizes

  . so the layers of atoms in an alloy are distorted

  . so in an allow the layers will slide over eachother less easily than in pure metals
• describe a method the student should use to compare the reactivity of an unknown metal and zinc using silver nitrate solution ( both metals are more reactive than silver. (4)


  . measure the temperature change

  . when each metal is added to the silver nitrate solution

  . with the same volume/concentration of solution

  . the greater the temperature change the more reactive the metal
• Explain why aluminum is extracted using electrolysis and not by reduction with carbon. (2)

  . aluminium is more reactive than carbon

  . carbon cant displace aluminium
• Describe a method to make pure dry crystals of magnesium sulfate from a metal oxide and a dilute acid (6)

  . Insoluble base= magnesium oxide, soluble salt= sulfuric acid

  . add SO4 to a beaker, gently warm it using a bunsen burner

  . add MGO a bit at a time, stir the solution until MGO stops reacting with the SO4 (MGO is in excess because excess solid sinks to the bottom)

  . filter out the excess MGO to get the salt solution using a filter paper and a funnel

  . heat the solution in evaporating basin, leave it to crystalise to form the salt

  . pat the crystals dry with filter paper
• Explain why an acid can be described as both strong and dilute (2)

  . strong because it completely ionises in aqueous solution

  . weak because there are small amount of acids per unit volume
• In group 0 elements, the boiling point increases as you go down the group
• Give the meaning of isotopes (2)

  . atoms with the same number of protons

  . but with different numbers of neutrons
• Explain what is meant by a weak acid (2)

  . produces hydrogen ions in an aqueous solution

  . but is only partially ionised
• Explain what is meant by a strong acid (2)

  . strongly ionised

  . in an aqueous solution, when dissolved in water
• Give 2 reasons why graphite is used for the electrodes

  . graphite conducts electricity

  . graphite is inert
• aluminium is produced by electrolysing a molten mixture of aluminium oxide and cryolite explain why a mixture is used as the electrolyte instead of only using aluminium oxide (2)

  . the mixture has a lower melting point than aluminium oxide

  . so less energy is needed
• Explain why the positive electrode in the extraction of aluminium oxide must be continually replaced (3)

  . the electrode reacts with oxygen

  . the electrode is carbon

  . so carbon dioxide is produced
• Gallium was discovered 6 years after Mendeleev published his periodic table. Give 2 reasons why the discovery of gallium helped Mendeleev's periodic table to become accepted. (2)

  . Galium fitted in the gap Mendeleev left

  . gallium properties were predicted correctly by Mendeleev
• Which scientist first suggested that electrons orbit the nucleus at specific distances?

  Niels Bohr
• Give the correct reason why Mendeleev reversed the order of some pairs of elements

  so their properties matched the rest of the group
• How did Mendeleev arrange the elements?

  atomic weight
• A student suggested Mendeleev’s reason for reversing the order was to arrange the elements in order of atomic number. Explain why the student’s suggestion cannot be correct. (2)

  . atomic number= number of protons

  . and protons were not discovered until later
• Describe 3 differences between the nuclear model of the atom and the plum pudding model (3)

  . The nuclear model is made of mostly empty space

  . In the nuclear model, the mass is concentrated in the nucleus

  . in the nuclear model, the electrons and nucleus are separate
• Niels Bohr adapted the nuclear model. Describe the change that Bohr made to the nuclear model (2)

  . electrons orbit the nucleus

  . electrons are at specific distances from the nucleus
• Describe how the process of distillation produces pure water from salt solution (4)

  . solution is heated, the part of the solution that has the lowest boiling point evaporates first

  . The water evaporates

  . The vapour cools in the condenser

  . the vapour turns back into a liquid

  . pure water is collected in the beaker
• The mass number is the number of protons plus nucleus
• Evidence fro the alpha particle scattering experiment led to a change in the model of the atom from the plum pudding model. Explain how (4)

  . Most particles passed straight through the gold foil

  . so the mass of the atom must be concentrated in the nucleus

  . some alpha particles were reflected

  . so the atom has a positively charged nucleus
• Chadwick's work led to a better understanding of isotopes, explain how this led to a better understanding. (3)

  . Chadwick provided the evidence to prove the existence of neutrons

  . This was necessary because isotopes have the same number of protons

  . but different number of neutrons
• How do you calculate the relative atomic mass?


  isotope mass x isotope abundance/ 100
• Give one limitation of using a dot and cross diagram to represent an ammonia molecule.

  It is 2 dimensional / doesn't show the shape
• Give 2 observations you could make when a small piece of potassium is added to water (2)

  . potassium floats/melts/moves around

  . effervescence of potassium (fizz)
• Explain why the boiling point of the halogens increase going down the group (3)

  . The molecular mass of the halogens increase as you go down

  . so the intermolecular forces increase in strength

  . so more energy is needed to overcome the intermolecular forces
• Explain why the reactivity of the halogens decrease going down the group (3)

  . As you go down the group the outer electrons become further from the nucleus

  . so the nucleus has less attraction for the outer electrons

  . so an electron is gained easily
• Explain how carbon monoxide is produced when petrol is burned in car engines (2)

  . incomplete combustion

  . because of limited oxygen supply
• What shape is a buckminsterfullerene molecule

  spherical
• Give 4 uses of fullerene

  . anti-oxidants

  . drug delivery

  . catalysts

  . reduction of bacterial growth
• Suggest 2 reasons why fullerenes are suitable for its use (2)

  . unreactive

  . large surface area to volume ratio
• Name 3 other compounds that a student could add to hydrochloric acid to produce zinc chloride.

  . zinc carbonate

  . zinc oxide

  . zinc hydroxide