How was it?? It was easy for me im taking it next year so im happy
[I found it rather alright too, though the majority of people I've spoken to found it difficult. I'll type up what I believe will be the grade boundaries below! ]Markscheme of my answers
C4
1) atomic mass-12 (6 protons add 6 neutrons)
Electrons or protons cant remember was 4 (mass take away protons)
Configuration was 2.4 (6 electrons)
[3]
2) isotopes cause same atomic number but diff mass[3]
[I thought this was only 2 marks?][The following two questions focused on the advantages and disadvantages of super conductors. The first question asked you to recall two potential benefits of superconductors; any two of the following would have been acceptable-
Loss-free power transmission
Super-fast electronic circuits
Powerful electromagnets
The second question was worth one mark, and asked for one disadvantage of superconductors. Off of the top of my head, a disadvantage would be that they only operate at very low temperatures (below -268.8 degrees). 3)covalent bonds of cl and F should be two overlapping circles with one pair of shared electrons
[The question asked for you to draw a 'dot and cross' model for the bond between chlorine and fluorine. Although you could have drawn all of the electronic shells, you could have simply drawn the outer shell. In the past, drawing the outer shell has been acceptable for both marks.][2]
4)mendeleev put elements on cards and arranged in order of properties and weight. Idea not accepted till gallium discovered
[In 1869, Mendeleev arranged the elements in order in a table [1]. He noticed periodic changes in properties. From there, he was able to predict new elements [1].][2]
5)iodide -grey solid astatine -320-340 allowance i think
[I believe you also had to predict the melting point, though I'm not sure what it was.] [2]
6)less reactive down group 7 because outer shell gets further away from nucleus so harder to gain electron
[The nearer the outer shell is to the nucleus, the easier it is for an atom to gain one electron. The easier it is to gain the electron, the more reactive the halogen is.] [2]
7)[6]
it was copper chloride for compound A
because precipitate was blue with sodium hydroxide
compound B was iron (II) ...as precipitate was green i think cant remember
Word equation forgot
Balanced equation forgot
8) super conductor used for medical scanners and powerful computers power transmission doesn't lose energyDisadvantage expensive to maintain low cost doesn't work at room temp[3] [Mentioned above as an earlier question.]Missing question?
[There was a question following the dot and cross model which asked you to predict two properties of the compound. I'm not sure what I wrote, but the answer may have been something like low melting/boiling point due to the weak intermolecular forces?]C5
1)number moles is 0.08[1]
2)use reacting ratios to get 50g[2]
3)i got 300 dm3 which is 300000cm3[2]
[I'm not sure about this one.]4) titrations [6 mark]
- ph starts high
-ph decreases when acid added
-ph decrease most near end point
Concentration was
0.16 mol/dm3 or 0.08
Volume was
40 cm3/ 20cm3 i wrote both just in case but i think 20
5) they use less acid(/alkali ???) of 0.05 so less moles
Graph would be lower than the first one lezs steep and reaction end slightly slower[2]
6)catalyst[1]
7)temp compromise balance between yield and rate increases rate of reaction
[I believe you had to mention the fact that high temperatures force the equilibrium to the left, and because the equilibrium for the Contact process lies naturally to the right, this is detrimental. The high temperature is used to increase the rate of reaction, and, as you said, is a compromise.]Catalyst- increase rate not affect equilibrium
low Pressure cheap pressure affects yield
[High pressure is not required, as a high pressure would move the equilibrium further to the right, which is not necessary as the equilibrium already lies to the right. This saves money.][3]
8) Concentration is how many moles of acid are dissolved in 1dm3
Strength is how much it ionizes. [2]
9) Same volume produced cause same amount of reactants (and concentration). [1]
10) High concentration of hydrochloric acid and more hydrogen ionize which increases frequency of collision. [2]
11) White is chloride, bromide is cream, iodide yellow precipitates. [3]
Total:25 marks
C6
[6 mark]
- Oxidation is loss of electrons
- Reduction is gain
of electrons.- Copper gain electrons to form Cu atom
- Iron loses to form an iron ion
Word equations and balanced
[Formula equations? This would be required to achieve a level 2 or above.]2) Chlorine radical is regenerated so destroy more ozone it is a chain reaction. [2]
3) O3------O2+.... reaction 4??
[I chose reaction 2. Not too sure if that is right. [1]
[There was another 2 mark question which asked you to describe how the Cl atoms separate themselves from the CFC molecules, in terms of bonding and electrons.]4) Prediction wrong because it only changed with soap not the other one
[Washing up liquid.]. You had to be looking at water with calcium hydrogen carbonate (temporary hardness)[2]
5) Ester[1]
6) Bromine water / addition reaction alkene decolourises etc cant remember his results.
[Double bonded/ alkene decolourises to form a dibromino compound. This is an 'additional reaction'.] [2]
7) Margarine made from vegetable oil reacted with hydrogen and a catalyst.
[Hydrogen is bubbled through the oil at about 200 degrees using a nickle catalyst. The reaction turns the carbon-carbon double bonds into single bonds.][2]
Section D
1) On graph there was a decrease between 1977-1979 so this shows it was effective
[There was a sudden peak at 1977, though the concentration was shown to slow in it's increase, therefore it was effective- to an extent. This may have been a 2 mark question.]2)
[For the pie chart question, the second half of the question asked you to determine whether or not farming or residential use made the most impact of global warming; it was farming, as farming contributed the most to nitrous oxide and methane, which contribute to global warming. I believe the answer to the first one was nitrous oxide, but I'm not entirely sure what I wrote.]3) B more land more crops so more fertilizer needed
[There was less agricultural land available in country B than country A, so more fertilizer was used perhaps to increase the crop yield to sustain the country.]