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# A-level Chemistry Revision Squad! watch

1. guys what do you think the 8 markers are gonna be like based on those practicals
2. Can somebody help with this, pretty pretty pretty please?

Which of the following contains the most chloride ions?
A 10cm3 of 3.30X10^-2 moldm^-3 aluminium chloride solution
B 20cm3 of 5.00X10^-2 moldm^-3 calcium chloride solution
C 30cm3 of 3.30X10^-2 moldm^-3 hydrochloric acid
D 40cm3 of 2.50X10^-2 moldm^-3 sodium chloride solution
3. (Original post by angellll)
Can somebody help with this, pretty pretty pretty please?

Which of the following contains the most chloride ions?
A 10cm3 of 3.30X10^-2 moldm^-3 aluminium chloride solution
B 20cm3 of 5.00X10^-2 moldm^-3 calcium chloride solution
C 30cm3 of 3.30X10^-2 moldm^-3 hydrochloric acid
D 40cm3 of 2.50X10^-2 moldm^-3 sodium chloride solution
I'm guessing you'll have to find the moles of each one and see which is the highest
So from what I've worked out, you both get 1 mole for B and D
And from the molecular formula, I'll go with B because you get CaCl2 and not NaCl which is 2 moles of chlorine
Is that right?
I'm totally guessing lol

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4. (Original post by Bloom77)
I'm guessing you'll have to find the moles of each one and see which is the highest
So from what I've worked out, you both get 1 mole for B and D
And from the molecular formula, I'll go with B because you get CaCl2 and not NaCl which is 2 moles of chlorine
Is that right?
I'm totally guessing lol

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Yes it is, thank you. I got up to the bit where B and D had 1 mole. I just didn't know where to go from there.
5. (Original post by PlayerBB)
Usually, you round your answer according to data significant figures that is given in the question, if the question asked like there is 0.01 mol of Mg and 1.2 mol of Na, the both number of moles is to 2 s.f then you'll have to round your answer to 2 s.f , when the data in the question was given to different s.f, you have to round your answer to at least 3 s.f , and that's why in this case the mark scheme would say, accept any answer except to 1s.f which means if you have rounded your answer up to 1 s.f then it is rejected
Thankyou!

SO just to confirm, my answer of 0.15 vs 1.149 is okay because I rounded to 2 sf rather than just 1?
6. (Original post by NimbleNeil)
Thankyou!

SO just to confirm, my answer of 0.15 vs 1.149 is okay because I rounded to 2 sf rather than just 1?
Np!

And yeah it is fine!
7. How many practical questions come up in the exam for paper 1
8. To calculate empirical formula first work out the number of moles of carbon and hydrogen. You do this by dividing the percentages of each element by the ram. So carbon would be 82.8/12. Then Hydrogen is 17.2/1

Then divide by the smaller decimal to get a 1:x ratio of some sort. Remember when you do that you cannot have a decimal so either round down or up. That will give you the empirical formula. Then look at the ratio between the empirical and molecular formula. It will be an easy whole number.
9. (Original post by Bloom77)
I'm guessing you'll have to find the moles of each one and see which is the highest
So from what I've worked out, you both get 1 mole for B and D
And from the molecular formula, I'll go with B because you get CaCl2 and not NaCl which is 2 moles of chlorine
Is that right?
I'm totally guessing lol

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Ok. So you have calculated the number of moles. B is calcium chloride and this has 2 chloride ions. So the number of moles has to be divided by 2. So the true concentration of chloride will be half the amount you calculated. As D is sodium chloride there is only one chloride ion so that will be the true concentration.

From all of that the answer you need is d
10. For the AS AQA new spec, where can I find questions related to the practicals we did?
11. can some one quickly go over...

1) the bond enthalpy diagram with the arrows i don't get how to draw them

2) The new..
Electron Impact Ionisation
Electro spray Ionisation

3) explain why a 2+ ion has a different m/z and how to work it out

pls i dont understand any of this literally all i need to know then ill be ready

12. I got this picture from Doc Brown and i understand why there are 5 peaks but my question is:
how do you know how long to draw them (i.e. what their relative intensities are) especially the last three peaks
13. (Original post by FemaleBo55)
I was looking for a Chemistry Revision Thread but there were not any so I decided to make one

Feel free to ask questions regardless of your exam board (because chemistry is chesmitry), and we'll all be happy to help!

http://www.thestudentroom.co.uk/show...1#post65057641

im in desperate need of help..
http://www.thestudentroom.co.uk/show...1#post65057641
IM IN DESPERATE NEED OF HELP..
15. pls help me with this questionthe answer is 0.01/6.26 x100i know how to get 6.26 which is the mass of crucible and ore(g) - mass of crucible pls help me

16. How would you name this?

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17. (Original post by Glavien)

How would name this?

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2-methylethyl 2-methylpropanoate? my guess anyway

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18. (Original post by Hunnybeebee)
2-methylethyl 2-methylpropanoate? my guess anyway

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I thought it would be:
1,2-dimethylpropyl 2-methylpropanoate

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19. Could someone help me describe the influence that non-standard conditions have on corrosion in terms of standard electrode potentials. Any help would be great, even a link would be appreciated.
20. (Original post by Glavien)
I thought it would be:
1,2-dimethylpropyl 2-methylpropanoate

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I need to look at the diagram properly :'( look like a fool lol

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