p1

• errors

  systematic- consistent and repeatable error that occurs due to faults in equipment, experimental design, or technique- affect all measurements in the same way, making them consistently too high or too low

  random- unpredictable variation in measurements caused by small, uncontrollable factors- make results scatter above and below the true value

  zero- occurs when a measuring instrument does not start from exactly zero, leading to inaccurate readings
• variables

  independent- change

  dependent- measure

  control- same
• 2 substances which can be reacted with a dilute acid to make zinc chloride

  zinc, zinc oxide and zinc hydroxide
• the reaction between hydrogen and chlorine is exothermic. explain why this reaction releases energy to the surroundings

  energy is needed to break bonds and energy is released when bonds are broken and the energy released is greater than the energy needed
• explain why methane [gas] and ploy(ethene) [solid] exist in different states at room temp

  methane has smaller molecules so have weaker imf forces and so need less energy to over come--> b.p and m.p are lower

  [vice versa]
• weak acid in terms of ionisation

  (the acid is only) partially ionised (in aqueous solution)
• which combination of changes increases the conc of an acid

  the mass of acid dissolved is doubled and the volume of the solution is halved
• in titration what indicator is added to an alkali in a flask

  phenolphthalein from pink to colourless
• which ion makes a solution alkaline

  OH-
• which element has the same electronic structure as the chloride ion

  (electron wise- full outer shell) Argon
• why do alloys not conduct electricity as well as pure metals, answer in terms of structure and bonding

  alloys have a disrupted/ irregular structure meaning it is harder for delocalised electrons to move through the alloy freely
• suggest 1 reason why sodium is not a product of electrolysis (NA+ and Al+ ions)

  sodium is more reactive- the least reactive is the product
• how was oxygen produced from water during the electrolysis of this aqueous solution (hydrogen -ve electrode, oxygen +ve electrode)

  water molecules break down to produce OH- and H+ ions

  OH- attracted to +ve electrode and H+ attracted to -ve electrode

  OH- discharged / oxidised to give oxygen
• nanoparticles of titanium dioxide are used instead of fine particles of titanium dioxide for coating self- cleaning windows

  higher s.a. to volume ratio and less material needed for the same effect
• test to identify chloride ions

  add nitric acid and silver nitrate into chlorine ion solution

  positive: white precipitate
• why would a student heat an evaporating dish and contents until the mass did not change?

  to evaporate all the water
• 2 words which describe the reaction between hydrogen gas and oxygen gas

  combustion and reversible
• why does the yellow dye and red dye travel different distances in experiment 1. refer to forces attraction between the dyes and the chromatography paper

  the yellow dye has weaker forces of attraction so it is more soluble and can travel further up the paper
• explain why the yellow dye is in different positions in experiment 1 and in experiment 2 despite using the same type of chromatography paper

  • there are different solvents (name them)- water and ethanol
  • yellow dye is more soluble in ethanol
  • so yellow dye travels further
• compare purity of orange dyes A and B

  A is impure as it is made of red and yellow dyes so it separates

  B is pure as it doesnt separate
• explain how oxides of nitrogen are produced when burning fossil fuels

  high temp is needed to break triple N bonds

  when they break, the N bonds with O
• explain one positive on the environment of burning hydrogen rather than natural gas as a fuel

  no $CO_2$ is produced which is better for the environment as greenhouse gasses aren't released and so sea levels don't rise
• one negative impact on the environment of burning burning hydrogen rather than natural gas as a fuel

  more oxides of nitrogen are produced when burning which causes health problems such as respiratory diseases like asthma
• test for presence of sulfate ions in sulfuric acid

  test: add HCl and barium chloride

  positive: white ppt
• explain why percentage yield of sulfur trioxide in this reaction is greater if the pressure is higher

  pressure increases so the equilibrium shifts to the product as there are less moles in the product
• suggest 2 reasons why a higher pressure is not used when producing sulfur trioxide

  • more expensive as more energy is used
  • more dangerous as there is risk of explosion
• combustion products

  water and carbon dioxide
• which metal is most likely to be the metal in the metal oxide catalyst

  vanadium as it is a transition metal
• in a reaction profile, the reactants are higher than the products. what type of reaction is this and why?

  exothermic as energy is released into the surroundings
• describe how stronger and weaker bonds influence the rate of chemical reaction. use examples of bond to help you [5]

  • stronger bonds require more energy to break, increasing activation energy
  • higher activation energy means fewer successful collisions at a given temp
  • so takes longer for reaction to complete
  • weaker bonds require less energy to break so decrease activation energy
  • so takes less time for reaction to complete
• titration: state 3 possible sources of inaccuracy in this practical

  for each, suggest how you might improve the experiment to reduce inaccuracy

  • miscalculation when reading measurements from beurette- make sure it is at eye level and read from meniscus
  • not precise measurement of volume- use equipment with higher resolution
• aluminium is extracted by electrolysis, explain why it cannot be extracted by carbon [2]

  aluminium is more reactive than carbon so would not displace. they might end up reacting together instead
• name a metal extracted by carbon displacement

  iron, zinc, copper
• what shape is a buckminsterfullerene

  sphere
• explain how graphene contributes to its unique properties

  • single layer of carbon in hexagonal rings- slide over each other easily
  • each carbon has 3 covalent bonds, leaving on delocalised electron to carry charge and flow through structure- conducts electricity
  • has weak