AQA GCSE CHEMISTRY Unit 2 14th June 2017 Unofficial Mark Scheme

Poll

How did you find the test?

1) Line of Best fit (1 mark)
Smooth Curved line missing out the anomalie

1b)How much volume of gas was given off at 25 seconds? (1 mark)
between 13-15 depending on your best fit line

1c) After how many seconds did the reaction stop? (1 mark)
50 seconds

1d) What is the rate of reaction? (2 marks)
6/10 = 0.6cm^3 per second

1d) Control variables : (2 marks)
Same amount of time for each to react.
Same volume of hydroxide peroxide solution for each concentration
Same surface area of catalyst

1e) Explain what effects does increasing the concentration have on the rate of reaction. (3 marks)
= Rate increases. More hydroxide peroxide particles in the midst of water molecules (closer together)so more frequent collisions.

1f) Describe the effects of increasing the amount of catalyst on the results( what changes on graph) (2 marks)

EITHER
Catalyst increases rate of reaction therefore the line on the graph will be steeper and will level off quickly
OR
" If there is ENOUGH catalyst in the first place, then adding more catalyst will have no effect"

2) Explain why the properties of metals and thermosoftening polymers relate to their structure and bonding (6 marks)
Metals have layers -Can slide- Free moving delocalised electrons- Strong electro static attraction- So can conduct heat and electricity.
Thermosoftening polymers have no cross links, individual tangled chains are weak. Low MP and BP Weak intermoldecular forces allow it to be easily overcame (melted and remoulded).

3) Draw the dot and cross for oxygen

3a) What type of bonding is this?(1 mark)
Covalent

3b) Explain why Oxygen has a low boiling point? (2 marks)
It is a simple molecular substance which has strong covalent bonds but weak intermolecular forces. This means that the melting and boiling points are low because the molecules are easily parted from each other.

??) Why is Silicon dioxide used for the line of furnaces (3 marks)
Silica has one giant structure with covalent bonds and a very high boiling point. It is an abundant material very hard and strong.

??) Describe what happens to magnesium2+ and oxygen- to form magnesium oxide. (3 marks)
Magnesium ion loses 2 electrons and gives to oxygen. Oxygen ion gains 2 electrons from magnesium ion resulting in full outshells for both; turning them into an atom forming a compound.

??) Balance the equation (1 marks)
2mg+ O2 ----> 2MgO

??) Compare the two inks (3 marks)
compare the amount of colours they each have (2 marks)
they share one same colour (1 mark)
ink a travelled up higher because it was more soluable than b. (1 mark)

??) Why does Sodium not form at the negative electrode? (2 marks)
Sodium does not form because it is more reactive than hydrogen. Hydrogen ions have a positive charge so they are attracted to the negative electrode and gains 1 electron.

??) Half equation(1 or 2 marks?)
2Cl ---> Cl2(+) + 2e(-)

??) Tick the correct box. Why would the rate of reaction be greater than expected? (1 mark)
The intial temperature was too low (3rd box)

??) Describe and suggest a method for the students paper chromotography ink experiment. (3 or 4 marks?)

Get beaker and strip of paper and inks.
Draw a line around 5cm from the bottom of paper horizontally.
Blot once the different two inks on pencil line but spread out from each other. (on either side)
Curl the strip of paper and put in beaker.
Fill the beaker with water up just below the pencil line.

??) Describe a method of getting crystals from copper oxide and sulfuric acid: (3 or 4 marks?)

Mix copper oxide with sulfuric acid
Heat gently
Once done, filter out any remaining particulates in the solution
Then leave the solution to evaporate after lightly heating it
To form crystals

??) Calculate mass needed for copper oxide (3 marks)
7.95g

??) How are substances seperated in gas chromatography? (3 marks)
The mixture is vaporised, and carried through a chromatography column in an oven by an inert carrier gas such as nitrogen. The different compounds travel through the column at different speeds/have different retention times, so they separate out.

??) What information does a mass spectrometer show? (1 marks)
Relative formula mass and the percentage amount of it.

??) Why was the PH at the end of the reaction 14?(2 marks)
Only sodium hydroxide was left over and this means there were lots of OH- ions in solution and OH- ions cause alkaline conditions. There are only alkaline elements and compounds in the solution which makes the pH very alkaline.

??) What are nanoparticles? (1 mark)
Nanoparticles are particles between 1 and 100 nanometers in size.
OR "a few hundred atoms"

??) What can you can conclude about this reaction? (1 mark)
It is exothermic

??) Why has there been an increase in the production rate of Ethene?

Need answer.

??)Compare the relationship of wealth of countries and average ethene production and (something else) production.
Need answer

This is what I have so far from looking at the comments and some of my own answers. I will update corrections and if people remember more questions! There are still a few one/two marker questions missing. And does anyone remember the marks for the questions?

(edited 6 years ago)

Reply 1

BenJames01

1

Please add to this thread as I can't remember all of them

1) Line of Best fit
1b) between 13-15 depending on your best fit line
1d) 6/10 = 0.6cm^3 per second
1d) control variables : same amount of time
And same volume which might be wrong
1e) Inc in concentration = particles are closer together so more frequent and successful collisions so faster ROR
1f) Catalyst increase ROR

2) Metals have layers
Can slide
Free moving delocalised electrons
Strong electro static attraction
So can conduct heat and electricity
Thermosoftening polymer chains
Are weak
Low MP and BP
Melt easily
Return to original shape

3) Draw the dot and cross for oxygen

(edited 6 years ago)

Reply 2

Classof2017

6

Original post by BenJames01

Please add to this thread as I can't remember all of them

1) Line of Best fit
1b) between 13-15 depending on your best fit line
1d) 6/10 = 0.6cm^3 per second
1d) control variables : same amount of time
And same volume which might be wrong
1e) Inc in concentration = particles are closer together so more frequent and successful collisions so faster ROR
1f) Catalyst increase ROR

2) Metals have layers
Can slide
Free moving delocalised electrons
Strong electro static attraction
So can conduct heat and electricity
Thermosoftening polymer chains
Are weak
Low MP and BP
Melt easily
Return to original shape

3) Draw the dot and cross for oxygen

1d) I put temperature and volume of the peroxide
1f) Catalyst increases ROR, but does not increase the amount of product made, it just decreases time. It also lowers activation energy.

Reply 3

Nickwood1737£:

3

Class of 2017 didn't it say that they were changing the volume of peroxide each time ?

Reply 4

visi0nary

5

Pretty sure it wasn't line of best fit for the first question.

Reply 5

username2740239

12

Original post by visi0nary

Pretty sure it wasn't line of best fit for the first question.

It was.

Also what did people put for the tick box question near the end? Was it that the final temperature reading was too low because thats what i put

Reply 6

candy667

1

Ink question: ink a and b have two similar colours, ink a had 3 colours, ink b had 4colours (i think)

(edited 6 years ago)

Reply 7

f_20011

1

I put the initial reading was too high

Reply 8

Mitzy2811

1

Original post by Nickwood1737£:

Class of 2017 didn't it say that they were changing the volume of peroxide each time ?

I think it said concentration?

Reply 9

f_20011

1

Original post by candy667

Ink question: ink a and b have to similar colours, ink a had 3 colours, ink b had 4colours (i think)

Wasn't it that since ink a travelled higher up it was more soluble than ink B

Reply 10

visi0nary

5

Original post by _b_e_n_

It was.

Also what did people put for the tick box question near the end? Was it that the final temperature reading was too low because thats what i put

I'm so sure the graph looked something like this instead of a line of best fit :/

Guess I'll just have to see the question again to know for sure

I don't think so.

For 4)b) I think I'vs got 7.95

Reply 13

candy667

1

You could say that too

Reply 14

f_20011

1

Original post by visi0nary

I'm so sure the graph looked something like this instead of a line of best fit :/

Guess I'll just have to see the question again to know for sure

It was one smooth curve through all the points apart from the anomalie

Reply 15

PlanetFelix

7

Original post by BenJames01

Please add to this thread as I can't remember all of them

1) Line of Best fit
1b) between 13-15 depending on your best fit line
1d) 6/10 = 0.6cm^3 per second
1d) control variables : same amount of time
And same volume which might be wrong
1e) Inc in concentration = particles are closer together so more frequent and successful collisions so faster ROR
1f) Catalyst increase ROR

2) Metals have layers
Can slide
Free moving delocalised electrons
Strong electro static attraction
So can conduct heat and electricity
Thermosoftening polymer chains
Are weak
Low MP and BP
Melt easily
Return to original shape

3) Draw the dot and cross for oxygen

For question 1c it said when did the reaction stop which was around 40 seconds but i do not remember the exact number

Reply 16

number0

12

Pretty sure tick box was initial temperature measured was too low, and for line of best fit there was an anomaly you had to miss out

Reply 17

f_20011

1

The calculation question ?

Reply 18

king_english

5

Original post by f_20011

I put the initial reading was too high

Original post by _b_e_n_

It was.

Also what did people put for the tick box question near the end? Was it that the final temperature reading was too low because thats what i put

It was the volume of sodium hydroxide solution might be incorrect. It was because in the steps, it just said "add 50cm3 of sodium hydroxide solution", and it didn't say "measure" it first, like it did for the step of adding the other reactant. You were meant to pick up on that I think. So I'm pretty sure that was the right answer.