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AQA Chemistry C3 - Unofficial Mark Scheme

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Reply 20
Avatar for Mahrez
Mahrez
12
Original post by milolj
Will you lose a mark for saying 1623 rather than -1623?


I got -486 or something
Reply 21
Avatar for Fr3dg
Fr3dg
7
Original post by lilacpotato
Last question: Using graph, suggest and explain why 450 degrees C and 200 atmospheres are the conditions for the Haber Process (5 marks)


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Temperature is compromise between low for higher yield as exothermic is favoured, and rate as rate is faster with higher temperature. pressure is compromise between high for favouring ammonia producing reaction, and low for safety and cheaper running.
Original post by bod247
Its Rb because in group 1 (alkali metals), the Boiling point and Melting Point decrease as you go down. Rb was the last Alkali Metal so its the lowest Boiling Melting/Point.


I put iodine lmao
Original post by user2k16
the bond energy question I didn't get a minus (-) as it was an endothermic reaction ?


It was definitely an exothermic reaction which gave a negative enthalpy change and I'm 100%on this because at the start of the next question is said "this reaction is exothermic" lol
Reply 24
Avatar for Fr3dg
Fr3dg
7
Original post by CaptErin
They usually put the minus in brackets on the mark scheme like '(-) 1623' so you should be fine :smile:


You don't lose mark
Original post by bod247
Its Rb because in group 1 (alkali metals), the Boiling point and Melting Point decrease as you go down. Rb was the last Alkali Metal so its the lowest Boiling Melting/Point.

Yeah but fluorine was there and is a gas at room temperature whereas rubidium isnt
The fill in the blanks question was an acid catalyst and an eater right?
It's flourine because it's a gas at room temperature. Rubidium is a metal and therefore is not
Reply 28
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rajen
Original post by milolj
Will you lose a mark for saying 1623 rather than -1623?


I don't think so, i was looking at a mark scheme a couple of days ago for a similar question and it had the minus written in brackets
Original post by YAY GCSE
It was definitely an exothermic reaction which gave a negative enthalpy change and I'm 100%on this because at the start of the next question is said "this reaction is exothermic" lol

I am sooo blind
Original post by milolj
Will you lose a mark for saying 1623 rather than -1623?


No
Original post by TheAnon121
Post your answers below, and we'll get an unofficial mark scheme!

Random answers:
Bond energies: -1623 or -1276 - Not sure which one is right
Explain why: Energy needed making bonds was greater than energy released breaking bonds
Balance equation: 2 and 2 somewhere
Efficiency of Kettle: Hydrogencarbonate ions thermally decompose to calcium ions, then react with carbon to product a precitipates of calcium carbonate (limescale). Limescale is a bad conductor of electricity - more energy needed to heat water
Hard water cleaner q: Calcium and magnesium ions replaced by sodium and hydrogen ions
Benefits of hard water: contains calcium which strengthens teeth and bones
Element that has low boiling point (or something: Rb or F (not sure)
What happens in the mixture of gases? Ammonia is liquified, then cooled - Nitrogen and Hydrogen are recycled
Specific heat capacity: 3444J


For bond energies I am 100% sure it should be (-)1,276. I wrote out all the bonds underneath next to their bond energies, added up each side of the reaction and checked the numbers 3 times (I finished quite early so thought I'd count up each side again)


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Reply 32
Avatar for Fr3dg
Fr3dg
7
Original post by GCSEstudentt
I put iodine lmao


It's flourine, rubidium is solid at room temp flourine is gas at low temp.
For the titration question , i said to put the alkali in the burette and acid in the flask does it make a difference?
Reply 34
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arj2104
1
How many marks was the Specific Heat Capacity question
Reply 35
Avatar for Fr3dg
Fr3dg
7
Original post by Roquebrune2014
For bond energies I am 100% sure it should be (-)1,276. I wrote out all the bonds underneath next to their bond energies, added up each side of the reaction and checked the numbers 3 times (I finished quite early so thought I'd count up each side again)


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I am agree, I redo outside three time and -1276 is my answer
Reply 36
Avatar for milolj
milolj
2
Original post by bod247
Its Rb because in group 1 (alkali metals), the Boiling point and Melting Point decrease as you go down. Rb was the last Alkali Metal so its the lowest Boiling Melting/Point.


Sorry but the answer is indeed F (thank Google)
Original post by Lmemon123
For the titration question , i said to put the alkali in the burette and acid in the flask does it make a difference?


Nope they accept converse, you're fine:smile:


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Original post by milolj
Will you lose a mark for saying 1623 rather than -1623?


Not in GCSE
What did everyone get on that table question which asks about the changes of the solutions?
I got white precipitate for the calcium one, no change for both the water one, no change for one of potassium and for the other potassium one I wrote fizzing and bubbling which i think is probably wrong.

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