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# Official AQA AS Chemistry Unit 1 - 23Rd May 2013 Watch

1. To those sitting the Chemistry exam tomorrow I am sure you will do fine.

Good Luck and God Speeeeeeeed
2. am I the only who gets confused with the reactions for pollution and removing pollution??
Does anyone mind putting up the equations we are supposed to know?
3. (Original post by jodie.irwin27)
look at the jumps and count the number of electrons removed before the first jump. this will tell you the group number

e.g. period 2 element with successive ionisation energies of 1203 2304 3046 6078
the jump occurs after the third electron is removed, so it is in group 3 period 2, therefore it is Boron.
THANK YOU SO SO MUCH!!! I finally understand it you've saved my life
4. (Original post by Manni)
I get 0.0151 but the answer is 0.938
hi i just did the q:
Spoiler:
Show
the ratio is 1:2 therefore the moles of HCl is 2x0.0152=0.0304
number of moles=concentration x volume /1000
so rearrange to give (n x 1000) / V to give conc.
(0.0304 x 1000) / 32.4 = 0.938
5. Haha no worries!

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6. Good luck everyone!!

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7. Can someone tell me what the shape of AsCl4+ would be? how many bp and lp's ? (ANSWERED)
8. (Original post by The.Joker)
am I the only who gets confused with the reactions for pollution and removing pollution??
Does anyone mind putting up the equations we are supposed to know?
The ones that i know:
2CO + 2N0 ---> N2 + 2CO2
CaO/CaCO3 is used to remove SO2 as its basic and SO2 is acidic when dissolved.
There is a third one about using hydrocarbons but i dont get it so im leaving it out
9. (Original post by Revision-)
Can someone tell me how the shape of AsCl4+ has 3 bp and 1 lp. I thought it would have 4 bp and 1 lp or is it because of the +, you minus a Cl?
As has 5 outer electrons.
It's making 4 bonds so take away 4
5-4 = 1
positive charge so take away one electron, so there's no lone pairs.

So AsCl4 has 4 bp 0 lp
10. (Original post by Revision-)
Can someone tell me what the shape of AsCl4+ would be? how many bp and lp's ?
the way i do it:
As is in group 5 and has 4 Cl's attached=5+4=9 minus 1 for plus=8 so the shape is tetrahedral.
If it was a munus sign, you'd add one...if that makes sense?
11. yh thanks I looked at the wrong question in the Jan 13 paper, when it should have been to draw AsCl3 which it is just 3 bp and 1 lp lol.
12. (Original post by Revision-)
Can someone tell me what the shape of AsCl4+ would be? how many bp and lp's ?
I'm not good at this topic but I'll try .
So As has 5 electrons on its outer shell.and there are 4 electrons from 4 Chlorines.[one provided by 1 chlorine].since there's a + charge that means As has lost one electron so now has 4 in total .4 electrons on As + 4 electrons from the Chlorines = 8 electrons .we divide 8/2 = 4 to find the number of bonding pairs of electrons present.There are 4 bonding pairs and no lone pairs because there are 4 pairs of electrons .Remember 4 bonding pairs form a tetrahedral shape with bond angles of 109.5 .hope I helped I did the same question this afternoon

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13. (Original post by jodie.irwin27)
basically

atomic radius across a period: decreases. increased nuclear charge meaning stronger nuclear attraction. Shielding remains the same.
(so due to the increased nuclear attraction, electrons are pulled in closer towards the nucleus, so the size decreases)

atomic radius down a group: increases. increased shielding so electrons are further away from the nucleus meaning a weaker nuclear attraction

ionisation energy down a group: decreases. Increased shielding so electrons are further away from the nucleas meaning a weaker nuclear attraction
(Which makes the outer electron more easier to remove)

ionisation energy across a period: increases. Increased nuclear charge meaning stronger nuclear attraction. Same Shielding.

note: ionisation energy across a period can decrease for certain elements.
for example, if an element enters a higher energy level, there the outer electron is further away from the nucleas as has more shielding (so is easier to remove)
so, Be with electronic structure of 1s2 2s2 and B with electron structure 1st 2s2 2p1.
ionisation energy decreases for B, as it is easier to remove. (see above explanation)

finally, ionisation energy can also decrease across a period due to electrons pairing. For example,
electronic structure of N: 1s2 2s2 2p3 and of O: 1s2 2s2 2p4
electron in the 2p orbital has paired, meaning there is repulsion

hope this helped...
This actually cleared a few things for me aswell Thanks!!
14. Good luck everyone! I won't be on tomorrow so I hope you all do great! We'll discuss tomorrow! G'night!

- Tom
15. can anyone exlpain this answer from jan 12? many thanks (Q7B)
16. haven't revised since Easter...cramming like crazy oh ****...i got a U in Jan now retaking if I get a U I won't be surprised...hate chemistry with a passion.
17. Hey just want to quickly check, what is the equation relating concentration, moles and volume?
18. (Original post by weevilspongebob)
haven't revised since Easter...cramming like crazy oh ****...i got a U in Jan now retaking if I get a U I won't be surprised...hate chemistry with a passion.
if you want, you can watch videos, although might take 2 hours maybe...
19. (Original post by hype)
Hey just want to quickly check, what is the equation relating concentration, moles and volume?
n=c x v

number of moles = concentration x volume

concentration - mol dm-3

volume - dm3
1dm3 = 1000cm3
20. (Original post by Tplox)
if you want, you can watch videos, although might take 2 hours maybe...<br />
<br />
<br />
thanks that's what I have been doing, watching loads of YouTube videos and its half one in the morning and surprisingly im.not sleepy..still Gunna wake up at six so I need to sleep. I am not worried about the exam since I am so horrificly bad at chem there is no hope... Good luck to everyone miracles..

Updated: May 28, 2014
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