AS Chemistry- helping each other out!

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hey everyone, can someone please help me with this?
when do you comment about electrons filling orbitals and when electrons fill subshells?
i don't quite know when to use with term :/

Electrons fill up orbitals. A subshell is a group of orbitals eg the 3p subshell contains 3 p orbitals each with up to 2 electrons in each orbital

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Reply 2221

blueberry389

what if they asked you, why is this element in the d-block? or why does S have a lower 1st IE than P? how would you answer these qs?

Original post by samb1234

Electrons fill up orbitals. A subshell is a group of orbitals eg the 3p subshell contains 3 p orbitals each with up to 2 electrons in each orbital

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Reply 2222

Feraligatr

Original post by ozzie2

Yeah I mean a B isn't too bad considering I literally thought I knew nothing about chemistry, but after revising I feel more confident apart from the bloody intermolecular bonding and stuff which is just so annoying. If I can get near full marks in the section B part of the paper which I really like it will bump up my grade :smile:

Btw you done the chem empa paper? I would really like the answers :biggrin:

Spoiler

Then you've done quite well considering that you haven't revised much then :five:

I won't. I just find it really really irritating to get so many people asking for EMPA and ISAs answers and stuff. I get loads of PMs asking for them and it boils my blood... :redface:

And anyway, I'm on Edexcel :lol:

Reply 2223

Cherry82

Original post by Georgiam247

Yeah that's what I meant, wow that's behind but its possible, you'll just need to put in a lot of work! You'll be fine :smile:

Lol its physically impossible to finish the book between now and then as I've got two other subjects. I'm doing terrible in my practicals too. This isnt going to end well.

Reply 2224

C0balt

Original post by Frosty_A

Guys/girls, this question has been bothering me for a while now, would really like some help, would be much appreciated.

0.85g of an indigestion tablet containing calcium hydroxide was was reacted with 50cm3 of 1.00M hydrochloric acid. the resulting solution was made up to 250m3 in a volumetric flask. 25cm3 of this solution required 30.80cm3 of 0.100M sodium hydroxide for neutralisation. calculate the per cent purity, by mass of the calcium hydroxide.

So I calculated the moles of sodium Hydroxide, by using n= cv, so n = (0.100 x 30.80/1000) =0.00308 Moles

NaOH + HCL -> Nacl + H20, so they react 1:1, the moles of HCl must also equal 0.00308 moles.

but now what do I do?

The moles of HCl you have calculated is the I reacted HCl.
Now answer those questions
How many moles of HCl are there in 250cm3?
How many moles of HCl were there initially?
How many moles of HCl reacted with calcium hydroxide?
What is the ratio of reaction between HCl and calcium hydroxide?
What is the molar mass of calcium hydroxide?
What is the mass of calcium hydroxide in the tablet?
What is the percentage purity by mass?

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Reply 2225

C0balt

Original post by blueberry389

what if they asked you, why is this element in the d-block? or why does S have a lower 1st IE than P? how would you answer these qs?

The last added electron of X is in a d orbital

S's last added electron is paired with another electron so there is a repulsion between the electrons which makes it easier to remove it.

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Reply 2226

Frosty_A

Original post by C0balt

ok so in the 250cm3, n=cv, so 1.00m x 250/1000= 0.25moles
initially, there was, 1.00M x 50/1000= 0.05moles

well 0.05 moles.

1:1

57

0.85,

erm....

Reply 2227

Dinaa

How do you work our percentage purity? :blushing:

Reply 2228

C0balt

Original post by Frosty_A

ok so in the 250cm3, n=cv, so 1.00m x 250/1000= 0.25moles
initially, there was, 1.00M x 50/1000= 0.05moles

well 0.05 moles.

1:1

57

0.85,

erm....

Sorry I meant uncreated HCl in the first sentence

You multiply your calculated moles of HCl by ten because 25cm3 was used out of 250cm3.
Volumetric flask business was AFTER HCl was reacted so you don't know the concentration of the HCl in volumetric flask

And ratio is
2HCl+Ca(OH)2 ---> CaCl2+2H2O so it's 2:1

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Reply 2229

C0balt

Original post by Dinaa

How do you work our percentage purity? :blushing:

In the question it's the (mass of Ca(OH)2/mass of tablet)*100

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Reply 2230

C0balt

Original post by Frosty_A

ok so in the 250cm3, n=cv, so 1.00m x 250/1000= 0.25moles
initially, there was, 1.00M x 50/1000= 0.05moles

well 0.05 moles.

1:1

57

0.85,

erm....

Do you follow this? ImageUploadedByStudent Room1430841353.156413.jpg

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Reply 2231

Dinaa

Original post by C0balt

Do you follow this? ImageUploadedByStudent Room1430841353.156413.jpg

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Dayum, you good :erm:

Reply 2232

Frosty_A

Original post by C0balt

Do you follow this? ImageUploadedByStudent Room1430841353.156413.jpg

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So, what you are saying is:

First we must work out the moles of Sodium Hydroxide. We then used the mole ratio, to determine, the same amount of moles of HCL was used.

Then you worked out the moles of the HCl of the 250cm3, to give us the moles within that volume.

then you worked out the moles in 50cm3 hcl of 1.00m concentration.

But how does taking away 3.08x10-2 from 0.05, give us moles reacted?

Reply 2233

ozzie2

Original post by Feraligatr

Then you've done quite well considering that you haven't revised much then :five:

I won't. I just find it really really irritating to get so many people asking for EMPA and ISAs answers and stuff. I get loads of PMs asking for them and it boils my blood... :redface:

And anyway, I'm on Edexcel :lol:

Haha yeah thanks, tbh chem isn't that bad it's just certain topics that I find hard.

Same here I have like 11 unopened messages atm on top of probably 15 others I opened all about the bio empa :/

Original post by Dinaa

Amen, will put a few words on my first post.

Edexcel ��

Scrub get on my level AQA is the one (apart from AQA maths)

Reply 2234

Dinaa

Original post by ozzie2

Haha yeah thanks, tbh chem isn't that bad it's just certain topics that I find hard.

Scrub get on my level AQA is the one (apart from AQA maths)

Psst gtfo b4 I rek u :erm:

Reply 2235

ozzie2

Original post by Dinaa

Psst gtfo b4 I rek u :erm:

Come on lad 1v1 me :angry:

Reply 2236

Feraligatr

Original post by ozzie2

Haha yeah thanks, tbh chem isn't that bad it's just certain topics that I find hard.

Scrub get on my level AQA is the one (apart from AQA maths)

I find the topics aren't that bad, its the actual exam, sometimes they word questions really weirdly

And just saying believe it or not, Edexcel is harder than AQA. :yep:

I'm on Edexcel by the way and AQA looks like fun compared to Edexcel :tongue:

Reply 2237

Dinaa

Original post by ozzie2

Come on lad 1v1 me :angry:

u'd get emotionally fekd
chemically rekt

^lol not srs :frown:

Reply 2238

ozzie2

Original post by Adamkahn

Anyone who's done the A2 bio or Chem will exchange info for AS bio and chem

I think someone called Adamkahn has, might wanna message him

Original post by Feraligatr

I find the topics aren't that bad, its the actual exam, sometimes they word questions really weirdly

And just saying believe it or not, Edexcel is harder than AQA. :yep:

I'm on Edexcel by the way and AQA looks like fun compared to Edexcel :tongue:

Yeah, they do and it sometimes is pretty confusing, but with more past papers, you see the trends and know what to put for the answer.
Tbh that's a good thing for me because I get an easy exam spec (although I am gonna fail anyway :s-smilie:

)

Reply 2239

Feraligatr

Original post by ozzie2

I think someone called Adamkahn has, might wanna message him

Yeah, they do and it sometimes is pretty confusing, but with more past papers, you see the trends and know what to put for the answer.
Tbh that's a good thing for me because I get an easy exam spec (although I am gonna fail anyway :s-smilie:

)

Yeah I guess :lol: