OCR Gateway B C4 C5 C6

Again, don't remember much, questions in the wrong order, contribute where you can. I'll edit in between my revision (I still have two exams left ew).
UNOFFICIAL MARK SCHEME
C4
- Metal ion was Mg 2+ (1)
- Molecular formula of compound formed = MgFl2 (1)
-Fill in the box question:
proton mass 1, charge 1
neautron mass 1 charge 0 (2)
- Atomic radius/mass question - C (1)
- Ammonia can't conduct electricity as there are no free ions to carry charge. It has a low melting point because of weak inter-molecular forces (easy to part) (4)
- Metal carbonate breaks down into zinc oxide and carbon dioxide, this results in a colour change (3)
- Atomic mass refers to the average mass of the nucleus of that element, number of neutrons+protons, compared to mass of 1/12th of the mass of an atom of carbon 12 (1)
- Atom is neutral as there is the same no. of protons as electrons, charges cancel out (2)
- Forgotten which group the question was referring to, but generally atoms in the same group have the same number of electrons in their outershell so all react to form ions with the same charge which makes them all highly reactive and gives them all similar properties (2)
- Suitable dot and cross diagram, oxygen forms a 2- ion, each sodium atom forms a 1+ ion (2)
- Chlorine was the second most reactive. The element that displaced chlorine was the most reactive as more reactive halogens displace less reactive ones. The third most reactive element was the one that had no reaction with the bromide+chloride solution, but displaced the iodine. The least reactive element was the one that made no reaction as it couldn't displace any of the other halogens meaning it was less reactive than all the other halogens. Cl2 + 2NaBr -> 2NaCl + 2Br (6)
- Element is in Group 6 (1)
- CaCO3+ HCl -> CaCl2 + CO2 + H2O (2)
C5
- This was one of the questions I think I got wrong: That Pete bloke was right because volume increased with experiment C compared to experiment A for the same time ( like at 1 minute there was a 5cm^3 increase from experiment A to B). I said the female was wrong as if you divided the volumes of experiment C by experiment A for one of the times you got something like 2.25 which wasn't exactly 2 so it could not have been double. (2)
- Percentage composition = 12/42 x 100 = 28.6% (2)
- Graph question, something like 22 and 20, involved reading off graph (2)
- 0.0009 Mol (2)
- Concentration would be 0.045 mol/dm^3 (2)
- Equilibrium question - rate of forward and backward reaction must be the same, caused by the reactant particles being used up in the forward reaction, concentration increasing on the right side, only works in a closed system (3)
- Method was mixing the two solutions from either test tube in a beaker, the lead iodide would precipitate out. You would then have to filter it using filter paper, use distilled water to wash away any soluble salts etc. There was also a balanced symbol equation I believe you had to write, some thing like:
PbNO3 + 2NaI -------> PbI2 + NaNO3 (I think this is wrong someone get back to me on this I don't remember lmao and I got this wrong in the exam anyway) (6)
- Mass of hydrogen = 0.004g (2)
- Equilibrium shifts to the right when oxygen is added (1)
Conditions of Contact Process:
-Vanadium Pentoxide (V2O5) Catalyst (1)
-High temp: 450C (1)
C6
- Iron + Water + Oxygen -> Hydrated Iron (III) Oxide (1)
- Fe3+ atom gains electrons (reduction), Mg atom loses electrons (oxidation). Reduction and oxidation are happening at the same time, hence REDOX. (2)
- Water hardness question - calcium sulfate for permanent (1)
- -Exothermic, energy of products lower than energy of reactants so energy is given out (1)
- Fuel cells question - I think it was 4H+ + O2 + 4e- -----> 2H2O (1)
- Soap question - liquid A as it showed a decrease in soap drops after boiling, fell to level needed for distilled water (2)
- Ozone layer question - previously used as coolants/refrigerants and had useful properties, but scientists found out it created a hole in ozone layer so Montreal Protocol was signed (could be shortened) (2)
- Alkanes replaced HFCs (1)
- The covalent bond between carbon and chlorine splits equally forming free radical (1)
- Detergent has a hydrophillic head, hydrophobic tail, head strongly attracted to water molecules, tail strongly attracted to oil molecules etc. Oil droplets surrounded by a coating of detergent which lifts oil off the stain. The guy was right to choose C, second most cost effective (lowest £ per wash) and also gave the whitest appearance, didn't fade etc. (6)
- Dry cleaning question : works by using a dry cleaning solvent instead of water, and the nylon has to be dry cleaned because water may damage the fabric/perhaps might be damaged by high temp involved in detergent cleaning (2)
- galvanizing involves coating iron in zinc which acts as sacrificial protection so it will lose electrons in preference to iron and also acts as barrier for air and water (2)
Section D
- Graphs show that the solubility decreases with temp, indian ocean warmer than arctic so less acidity (2)
- There should have been a seperate column for temp as temp. affects pH too (1)
- Maybe sample size should have been bigger, as in more years+ more readings should have been taking for each year to increase reliability (2)

(edited 6 years ago)

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Reply 1

azizkahdijaaaa

first question mg(2+)

group 6

c4
the atomic radius- C
the filling in the box- proton- 1 - +1
neutron-1 0

why does the atom stay neutral?
- charges cancel out
-same number of protons and neutrons

what is the atomic mass number?
-total number of neutrons and protons in an atom

describe the simple molecular structure?
low boiling point- weak intermolecular forcrs
-doesnt conduct electricity- no ions so cant carry charge

what does metal carbonate break down into?
metal oxide and carbon dioxide

Reply 4

rkho

the equation was Cl2 +2MgBr -> 2MgCl + Br2

Reply 5

sivayogan29

C4

Relative charge for proton and neutron were 1 and 0. Relative mass was 1 for both
Predict physical properties of ammonia. I wrote low melting point and can't conduct electricity, but think that's wrong (4 marks)
Radius and mass of atom = 10^-10 and 10^-23 (Option C)

C5
Percentage composition = 12/42 x 100 = 28.6%?
Graph question, something like 20 and 22
Equilibrium question - rate of forward and backward reaction must be the same, caused by the reactant particles being used up in the forward reaction, concentration increasung on the right side, only works in a closed system

C6

Water hardness question - calcium sulfate for permanent
Fuel cells question - I think it was 4H+ + O2 + 4e- -----> 2H2O
Soap question - liquid A (the one that showed a decrease in soap drops after boiling
Dry cleaning question : works by using a dry cleaning solvent instead of water, and the nylon has to be dry cleaned because water may damage the fabric
Ozone layer question - previously used as coolants/refrigerants and had useful properties, but scientists found out it created a hole in ozone layer so Montreal Protocol was signed (could be shortened)

OCR Gateway B C4 C5 C6

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