Unofficial Mark Scheme AQA GCSE Chemistry 14 June 2017Watch
IF I FORGOT A QUESTION PLEASE TELL ME AND I WILL ADD IT.
1) Smooth Curve
Must avoid the anomaly
1b) Amount of gas given off at 25 seconds?
13.5-14.5 I think
1c) How many seconds did it take for the reaction to stop?
50 seconds (because the line leveled off here)
1d) ROR at 10 seconds?
0.6cm^3 per second
1e) What variables must be controlled? (Not too sure)
Same amount of time recorded
Same capacity of gas syringe
1f) Explain what effects does increasing the concentration have on the rate of reaction.
Something alone the lines of:
o More particles within same space
o More likely to collide successfully
o Speeding up the ROR (Rate of reaction)
1f) What effect would increasing catalyst amount have on Figure 2?
Say what it does:
Lowers activation energy, particles need to collide with less force
So effect is:
Line will be steeper and reach max oxygen volume of 20cm^3 more quickly
The line will level off and flatten before 50 seconds as the reaction is happening faster.
2) Metal and thermosoftening properties and how they relate to structure
They are malleable and easily bendable when pure (atoms arranged in regular layers that can slide over each other when pressure is it put on them)
They have high melting and boiling points (the delocalized electrons in metals leave the atoms and move through the structure. Since they (electrons) leave the atom this gives the atoms a positive charge and of course electrons are negative, so the charges are opposite and forms an electrostatic attraction between the atoms and electrons - metallic bonding. This electrostatic attraction force is very difficult to overcome, hence the metals high melting and boiling point)
They can conduct electricity (delocalized electrons can carry charges and move throughout the structure of the metal while carrying the charge and passing it on)
They can conduct heat (electrons gain heat energy, begin to vibrate more and pass this vibration onto other electrons passing on the heat)
Easily melted (they have tangled polymer chains held together by weak intermolecular forces that are easy to overcome)
Can be used for recycling (once the intermolecular forces are broken, we can reshape it into the desired shape and after time the intermolecular forces will reform, causing the polymer to harden up in the shape we put it in)
Flexible (tangled polymer chains can slide over each other and move due to weak intermolecular forces)
A diagram which shows, 4 electrons being shared in the mid section (should be two crosses and two dots) and then 4 electrons on the outer shell of each oxygen atom that is NOT being shared.
a - i) State the type of bonding
Covalent (two Non metals)
a - ii) Why does oxygen have a low boiling and melting point?
Something along the lines of :
o Simple molecule
o Weak IM forces
o Easily overcome - low BP and MP
So answer like:
It is a simple molecule with each O2 molecule being held together by weak intermolecular forces that can be overcome easily when heated, so the boiling and melting point is low.
*I'm pretty sure you wont need to say what I said about the simple molecule, just talk about the IM forces and how they are easily overcome.
b - i) ???? cant remember
b - ii) Bonding between Magnesium and Oxygen
o Mg has 2 electrons outer shell, Oxygen has 6
o Mg will give two electrons to the oxygen atom so Mg will have +2 charge and oxygen will have a -2 charge
o Opposite charges attract forming electrostatic attraction
o This makes magnesium oxide
For fourth mark maybe?:
o Magnesium is oxidized, oxygen is reduced.
b-ii) Balance equation.
I think it was:
2Mg + O2 ---> 2MgO
c) Why silicon dioxide lines furnaces?
It is a giant covalent lattice (Silicon and Oxygen) full of strong covalent bonds that are difficult to overcome. This means it is heat tolerant and can be put in the furnaces without melting.
a - i) Student doing paper chromotography, give method he could use.
He could use a piece of paper and draw a line in pencil (pen ink contains compounds and would affect experiment) at the bottom of the paper. He could place his two compounds on the line and when he places it in the water/solution, the inks solubility and compounds within it will mean they move up to different heights and split into different colors. He can use a ruler to calculate things like Rf value.
a - ii) Compare the two colors (they were both black lol)
I said, ink B has more compounds as it had more dots and split more however ink a is more soluble because it moved higher up the paper.
b - i) How does gas chromatography separate substances?
In a column containing the vaporized substances, a carrier gas will push the substances through the column. Since they are different substances, each substance has different levels of attraction to the insides of the column and so they come out at different times - this is their retention time so they can be separated(time taken to come out).
b - i) What does a mass spectrometer help to identify? *not too sure
Molecular Ion peak
a - i) Describe a method for getting copper sulphate crystals from copper sulphate solution
So we can filter off any of the unreacted and unwanted base and collect just the solution.
We can then evaporate the water within the solution leaving behind just the crystals.
a - ii) Calculate mass of Copper Oxide needed to produce copper sulphate crystals of 24.95g.
249.5 is the RFM of the crystals, and the mass being produced is 24.95g which is just dividing the RFM by 10 and using it as grams, so do the same to copper oxide.
The RFM was 79.5.
249.5 ----> 24.95 is dividing by 10
79.5 -----> ? but it must be divided by 10, so 79.5 /10 = 7.95g
7.95g of CuO required.
Cant remember next part please tell me if you know lol
a - i) Why was the temperature change greater than expected?
Wrong measurement of solution
a - ii) State one conclusion that can be made from the students results
The reaction is exothermic
b - i) Describe the link between sulfuric acid production and ethene
Generally, the richer the country is the more ethene it produces, A produced 36,600 kilotonnes and F produced 650 kilotones.
Sulfuric acid production is much less dependent on wealth as F was the (4th highest producer out of 6) of Sulfuric Acid and it was not the poorest.
b - ii) Why has the production of ethene increased in the last 50 years?
New technology and equipment can be used to obtain it more efficiently/easily.
6) cant remember most of this question btw
??) What forms at the negative electrode and why is sodium not produced?
Hydrogen gas is given off, because sodium is more reactive than hydrogen, so it instantly reacts with the hydroxide ions in the solution to form sodium hyrdoxide instead of forming at the cathode.
??) Why was the pH 14?
Sodium hydroxide formed in the solution, and this is alkaline so the pH would be alkaline of course.