A-level Chemistry Revision Squad!
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Original post by PlayerBB
What do you mean by the amount of water like the volume or the number of moles of water that can be removed ? If the number of moles, then it is 0.1 moles, because 5.55g of anhydrous CaCl2 is used, it Mr is 111, the number of moles of CaCl2 is 0.05, the moles ratio of the CaCl2 to water is 1:2 so the number of moles of water used 0.1 which is the number of moles that will be removed from the organic liquid
It just says 'amount of water'... but it's okay I think I've got it now thanks
Original post by PlayerBB
What do you mean by the amount of water like the volume or the number of moles of water that can be removed ? If the number of moles, then it is 0.1 moles, because 5.55g of anhydrous CaCl2 is used, it Mr is 111, the number of moles of CaCl2 is 0.05, the moles ratio of the CaCl2 to water is 1:2 so the number of moles of water used 0.1 which is the number of moles that will be removed from the organic liquid
It's almost certainly moles as it's a bit of a hassle to convert into a volume, and also moles is the SI unit for the amount of substance
Original post by samb1234
It's almost certainly moles as it's a bit of a hassle to convert into a volume, and also moles is the SI unit for the amount of substance
Yeah, that's what I thought!!
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Original post by kiiten
Bump
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Original post by kiiten
0.9/3 not 0.9/2.1 . It's like if you had 10 sweets and eat 5, the percentage isn't 5/5 =100% it's 5/10 =50% so you need to divide by how much there is at the start
Original post by samb1234
0.9/3 not 0.9/2.1 . It's like if you had 10 sweets and eat 5, the percentage isn't 5/5 =100% it's 5/10 =50% so you need to divide by how much there is at the start
Right, thanks
Original post by K3001N
1.
has anyone done the enthalpy change isa for AS Chem AQA?
Do you mean the required prac? If so then yeah
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With the calcium sulfide lattice structure, why are the sulfide ions larger than the calcium ions when calcium has a larger relative atomic mass? Please help 
Original post by jack.lp.thompson
With the calcium sulfide lattice structure, why are the sulfide ions larger than the calcium ions when calcium has a larger relative atomic mass? Please help
Think about the number of electrons and the charge.
Original post by kiiten
Think about the number of electrons and the charge.
Wouldn't the number of electrons be the same? (same as argon) I don't understand why the sulfide ion would be larger. Please explain
Original post by jack.lp.thompson
Wouldn't the number of electrons be the same? (same as argon) I don't understand why the sulfide ion would be larger. Please explain
For calcium yes. Can you use the periodic table to find out what charge the sulfide and calcium ions will have? - (sorry im new to this 'helping people' thing so im trying to help without telling you the answer
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Haha don't worry about it. And well as it is Ca2+ and S2-, wouldn't two electrons be lost/gained from each element causing them both have the same electron configuration as argon? (20-2=18) (16+2=18)??? So confused! haha . Please could just tell me why the sulfide ion is bigger?? :O aha
. Please could just tell me why the sulfide ion is bigger?? :O ahaOriginal post by jack.lp.thompson
Haha don't worry about it. And well as it is Ca2+ and S2-, wouldn't two electrons be lost/gained from each element causing them both have the same electron configuration as argon? (20-2=18) (16+2=18)??? So confused! haha . Please could just tell me why the sulfide ion is bigger?? :O aha
. Please could just tell me why the sulfide ion is bigger?? :O ahaWell, sulfur is more electronegative than calcium due to trends in electronegativity increasing across the period and up the group. If you have studied electronegativity you will know that this is from nuclear charge, atomic radius etc.
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Ah ok. That makes sense now. Thanks
Original post by PlayerBB
What's the name of this compound?
- Just for reassurance
- Just for reassurance
Spoiler
ermmm.. I get N-methylethylphenylamine?? probs wrong :/
Original post by haj101
ermmm.. I get N-methylethylphenylamine?? probs wrong :/
But why N- , I was thinking also tho like methylethylphenylamine but then I thought like they're connected to N atom and not to the benzene ring so I got confused!
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Original post by PlayerBB
But why N- , I was thinking also tho like methylethylphenylamine but then I thought like they're connected to N atom and not to the benzene ring so I got confused!
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Aaah true... im SO sorry i got confused with naming N-substituted amides (when we use N-). I think you are right
Original post by haj101
Aaah true... im SO sorry i got confused with naming N-substituted amides (when we use N-). I think you are right
It's okay and I think you use the N only when acyl chloride react with amines then it will form N-substituted amides
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