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🧪 > Wrong Questions - C1 to C3 > Flashcards

Wrong Questions - C1 to C3 Flashcards

1
Q

Why is a reaction endothermic?

A
  • bond breaking is endothermic / bond breaking takes in energy/bond-breaking absorbs energy (1)
    bond making is exothermic / bond making gives out energy
  • bond making releases energy (1)
  • more energy taken in than is released / more energy
    absorbed than given out (1)
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2
Q

How do you know if a substance is an enzyme?

A
  • it removes organic materials only such as food and blood

- not paint etc.

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3
Q

How do you test for unsaturated fats?

A
  • test - add bromine (water) (
  • result - idea that bromine water loses its colour (1) – this mark is dependent on the correct reagent or a
    near miss e.g. bromide
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4
Q

Describe the process of crystallisation:

A
  • solution heated until saturated (no more solute can be dissolved at that temp)
  • crystals form
  • lower heat = more crystals form as solubility increases
  • use filtration to separate the crystals and pat dry
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5
Q

What is the empirical formula?

A
  • the simplest whole-number ratio of atoms each element in a compound has
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6
Q

How does the melting point change in impure and pure substances?

A
  • m.p. of impure is less than pure

- b.p. of pure is less than impure

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7
Q

What is an allotrope?

A
  • diff form of element in the same state and with a different atomic arrangement
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8
Q

What makes something malleable?

A
  • particles can easily change position in a lattice
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9
Q

What makes something brittle?

A
  • substance can crack if an external force is applied
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10
Q

What is a disadvantage of low percentage yield?

A
  • waste a lot of starting material/wastes reactants (1)
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11
Q

How did Geiger and Marsden’s experiment tell us about the atomic structure?

A
  • Fired alpha particles at gold foil (1)
  • Geiger and Marsden’s experiment gave unexpected
    results / some alpha particles rebounded (1)
  • led to theory of nuclear atom / idea of atoms having
    a nucleus (1)
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12
Q

What’s a disadvantage of using universal indicator?

A
  • does not give a sudden colour change / colour

changes slowly / continually changes colour / (

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13
Q

Why should scientists work in groups?

A
  • can share ideas / have different views (1)
  • can evaluate ideas / check results / can compare
    results (1)
  • can collect more evidence (in a shorter time) / more
    productive / can do more approaches / can work
    faster / more ideas can be tested (1)
  • can share cost of research (1)
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14
Q

Describe endothermic reactions:

A
  • temp decreases
  • heat energy is taken from surroundings
  • bond breaking is endothermic
  • energy used to break bonds is more than the energy released by forming bonds
  • if not enough energy, the reaction may not start (activation energy)
  • positive energy change
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15
Q

Describe exothermic reactions:

A
  • temp increases
  • heat energy is given to surroundings
  • bond forming is endothermic
  • energy released by forming bonds is greater than the energy needed to break them
  • if not enough energy, the reaction may not start (activation energy) = activation energy
  • negative energy change
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16
Q

How is a pH meter used?

A
  • calibrate
  • adjust the reading to pH of the buffer solution
  • wash prove
  • place probe in a test solution
  • read the reading
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17
Q

How can you make soluble salts using acid/ alkali reactions?

A
  • can’t add excess alkali to acid and filter out what’s left as the salt is soluble and would be contaminated with excess alkali
  • thus need to titrate the solution with an indicator
  • carry out reaction with exactly the right proportions, without indicator as you now know exact volumes = salt is not contaminated
  • slowly evaporate water and leave the solution to crystallise and filter off solid and dry
  • SALT MADE IS AQUEOUS
18
Q

How can you make soluble salts using an acid and an insoluble reactant?

A
  • need to pick and acid, and a metal/ insoluble base (oxides/hydroxides of metals)
  • add an excess of base to acid = soluble salt and water - finished when excess solid sinks to bottom (may need to heat mixture)
  • filter of excess solid to get salt and water solution
  • heat solution to evaporate water and leave concentrated solution to cool and crystallise
  • filter off solid and leave to dry in warm over/desiccator
  • SALT MADE IS AQUEOUS
19
Q

How can you make insoluble salts using a precipitation reaction?

A
  • pick 2 soluble salts
  • add a spatula of 1st salt (Lead nitrate) to the test tube and add deionised water to dissolve it - shake and do the same to the 2nd salt (sodium chloride)
  • tip 2 solutions into small beaker and stir - salt should precipitate out
  • put folded filter paper into funnel and stick in conical flask
  • put beaker content into flask and make sure solution doesn’t go over the paper as thus less mass made
  • swill beaker with deionized water and tip into funnel
  • rinse contents of filter paper with deionized water and scrape lead nitrate into fresh filter paper and leave to dry
  • make sure reaction is complete before filtering and dry in desiccator or warm oven (NOT Bunsen Burner)
  • SALT MADE IS SOLID
20
Q

What is a non-inert electrode?

A
  • changes or decomposes into the electrolyte
21
Q

How does the electrolysis of purification of copper work?

A
  • anode = impure copper - mass decreases as copper dissolves
  • cathode = pure copper - mass increases as copper deposited
  • electrolyte = copper sulfate - collects impurities
  • metal ions from the electrolyte discharge on the surface and metal ions leave the anode to replace discharged ions and decompose to CU2+ ions in the electrolyte till the anode is used up
22
Q

What happens at the anode in a cell?

A
  • oxidation

- 4OH- –> 02+ 2H20 + 4H+

23
Q

What are the advantages of a high atom economy?

A
  • more sustainable / make less or no waste products (1)
24
Q

Why do strong and weak acids both make the same no. of moles of H2?

A
  • they have the same no of moles of metal (e.g. magnesium), which is the limiting reactant
25
Q

How does an increase in pressure affect the rate of reaction?

A
  • more crowded
  • are closer together
  • more molecules in the same volume
  • number of collisions per second
26
Q

How does an increase in concentration affect the rate of reaction?

A
  • more crowded
  • acid particles are closer together
  • more acid particles per unit volume
  • more (successful) collisions per second
27
Q

What is the difference in reaction between sodium and water and sodium and butanol?

A
  • sodium and water makes an alkali and H2

- sodium and butanol makes a salt and H2

28
Q

Why may the right amount of ester not be made? Is it due to the reaction reaching equilibrium or the reactants running out?

A
  • all acids and alcohols are not used up as the amount of reactants stay the same
  • even if it reaches equilibrium, the rate of the forward reaction is equal to the rate of the backward reaction
  • reaching equilibrium doesn’t mean reactions stop
29
Q

Why may sulfuric acid be added in reaction?

A
  • acts as a catalyst to speed up reactions

- lowers the activation energy

30
Q

What parts of a titration make it more accurate?

A
  • add alkali in conical flask with pipette
  • read from meniscus
  • drop by drop in the end
  • always swril mixture
  • when colourless, stop instantly
  • repeat three times - the first one is a rough titre
  • until concordant titres (within 0.1cm cubed)
31
Q

Why does gunpowder not react until it’s lit?

A
  • when it’s lit, energy is transferred to it which is the activation energy
  • this is needed to break the bonds
32
Q

What does diatomic mean?

A
  • 2 atoms or pairs of atoms in each molecule
33
Q

What is the difference between a by-product and a waste product?

A

by-product/oxygen has another use; ORA(1)
the waste product is thrown away / must be disposed of;
(1)

34
Q

Why are the relative atomic mass (Mr) of some elements are whole numbers but others aren’t?

A
  • Mr of an element is the average of the mass numbers of all the atoms of that element
  • if they only have one isotope - Mr is equal to the mass number to that number of atoms
  • but if they have more than one isotope which has different quantities then their average isn’t a whole number
35
Q

Why is the decrease in mass calculated in electrolysis not the increase?

A

Because newly deposited copper can flake
off the cathode easily, leading to mass
values that are too small

36
Q

Why do reaction rates decrease near the end?

A
  • acid particles used up
  • so concentration decreases
  • less frequent collisions / fewer collisions per second
  • so rate decreases/reaction slows down
37
Q

Why is excess added in neutralisation reactions?

A
  • to make sure the substances react
38
Q

What is a strong acid?

A
  • completely / fully ionised

- in an aqueous solution or when dissolved in water

39
Q

Why may a fertiliser cost more than the other?

A
  • more stages
  • uses more energy
  • uses more raw materials
  • takes longer
40
Q

Compare the plum pudding and the nuclear model:

A
  • both have positive charge, both have (negative) electrons, neither has neutrons
  • differences:

plum pudding model:

  • ball of positive charge (spread throughout)
  • electrons spread throughout (embedded in the ball of positive charge)
  • no empty space in the atom
  • mass spread throughout

nuclear model:

  • positive charge concentrated at the centre
  • electrons outside the nucleus
  • most of the atom is empty space
  • mass concentrated at the centre

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