A-level Chemistry Revision Squad!

The reactions of aqueous ions in solution.docx19.7KB

Original post by Zain-A

The question asks to name this compound, it says the answer is 2-ethoxybutane, but should it not be 2, methyl-ethoxypropane?

Also just noticed this, how tf does the CH2 carbon have 5 bonds?!? Is this question completely wrong or am I missing something major here?

That is seriously weird.
You're right , but to be pedantic with numbers and ordering, I would name that 1-ethoxy-2-methylpropane

This question is completely wrong.
I think they've swapped the CH₂ and the CH around. Either way that is definitely NOT butane.

My guess is that this is a printing error, or typing error. The methyl group should actually go on CH. In that case, yes it would be 2-ethoxybutane.

Reply 302

MedSchoolDreams

1

Original post by PlayerBB

Are you sure uou wrote it correctly, because the number of electrons are not balanced

For the first equation, it +15 on the first side and +20 on the second

Sorry, I submitted an image before but it's not deleting so otherwise it would be correct if the number of electrons were correct and I thought you wrote 5V3 + and not 5V 3+ so excuse this mistake

Yeah it was a made up equation, so that's probably why the electrons are wrong, but you have given me the answer about what to do with the H+ and the H20's so thankyou :smile:

Reply 303

PlayerBB

17

Original post by MedSchoolDreams

Yeah it was a made up equation, so that's probably why the electrons are wrong, but you have given me the answer about what to do with the H+ and the H20's so thankyou :smile:

Glad I helped and No problem :smile:

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Reply 304

chzm

10

Original post by RMNDK

Careful..
Your Sodium isn't balanced.
i.e. should be Na₂SO₃

Also, how does SO₂ act as a base and an acid? It's not amphoteric; only an acidic oxide.
Are you sure you weren't thinking of SiO₂..?

yeah my bad! its can only acidic :smile:

sorry i was thining of silicon dioxide haha

Reply 305

MedSchoolDreams

1

Hi guys,

I have made this document with all the reactions of aqueous transition metal ions as part of my revision and I thought I'd share. I am going to use this and get my mum to read out the sub headings and I will recite the equation and the colour of the resulting complex.

Hope this helps some people :smile:

(edited 8 years ago)

Reply 306

VividBandicoot

18

Why does propan-2-ol have greater enthalpy than butan-2-ol? Does entropy not increase as the molecule size increases?

Reply 307

VividBandicoot

18

Original post by RMNDK

That is seriously weird.
You're right , but to be pedantic with numbers and ordering, I would name that 1-ethoxy-2-methylpropane

This question is completely wrong.
I think they've swapped the CH₂ and the CH around. Either way that is definitely NOT butane.

My guess is that this is a printing error, or typing error. The methyl group should actually go on CH. In that case, yes it would be 2-ethoxybutane.

Thanks for the help, one last thing, what does the 1-ethoxy or 2-ethoxy mean? I thought you just write methoxy or ethoxy etc etc and don't use numbers?

Reply 308

Original post by Zain-A

Thanks for the help, one last thing, what does the 1-ethoxy or 2-ethoxy mean? I thought you just write methoxy or ethoxy etc etc and don't use numbers?

The numbers indicate the carbon atom the group is bonded to.

An ether functional group is just like any other group, like a halogen group or an alkyl group. So treat it it's numbering just like you number halides, or methyl groups or whatever.

It's not like carboxylic acids which don't need the number.

For instance, going back to this

if I put the [O - C₂H₅] on the middle carbon of the propane (the one with the CH₂ that really should be CH), that now becomes 2-ethoxy-2-methylpropane.

So I need to specify the location of the alkoxy group if it potentially can be repositioned elsewhere.

Reply 309

Original post by MedSchoolDreams

Hi guys,

I have made this document with all the reactions of aqueous transition metal ions as part of my revision and I thought I'd share. I am going to use this and get my mum to read out the sub headings and I will recite the equation and the colour of the resulting complex.

Hope this helps some people :smile:

There are some mistakes in your equation of Co²⁺ with NH₃.
You also might want to give the colour of [Co(H₂O)₆]²⁺before it is oxidised by oxygen.

How come you haven't included the equation of Fe³⁺ with excess OH^-?
The precipitate will dissolve in concentrated NaOH.

Reply 310

Can someone help me with this question, i got 0.025 which is D but the answer in the marking scheme is A.thanks

and this question too

Original post by djmans

Can someone help me with this question, i got 0.025 which is D but the answer in the marking scheme is A.thanks

Hi

First you need to find the moles of Na2CO3: so we use the equation mass/Mr the Mass is 10.6 and Mr is 106. We divide 10.6 by 106 to get us 0.1 moles.Now that we have the moles we use the volume of the solution to help us find out the concentration: the equation is moles/volume so we divide 0.1 by 0.25 (we need to convert to dm3) to get us a concentration of 0.4.Hope that helps :smile:

Reply 313

Original post by haj101

Hi

First you need to find the moles of Na2CO3: so we use the equation mass/Mr the Mass is 10.6 and Mr is 106. We divide 10.6 by 106 to get us 0.1 moles.Now that we have the moles we use the volume of the solution to help us find out the concentration: the equation is moles/volume so we divide 0.1 by 0.25 (we need to convert to dm3) to get us a concentration of 0.4.Hope that helps :smile:

thanks i found the molar mass but messed up the next step.
:smile:

Reply 314

username1133132

15

Original post by djmans

and this question too

The answer is 82 KJ/mol-1:
82+419+122+(-349) + (-711)= -437

Reply 315

Original post by haj101

The answer is 82 KJ/mol-1:
82+419+122+(-349) + (-711)= -437

and also how to identify whether a compound is ionic or covalent or dative
eg: Strontium chloride.etc

Reply 316

username1133132

15

Original post by djmans

and also how to identify whether a compound is ionic or covalent or dative
eg: Strontium chloride.etc

You need to be able to identify the metal and non metal elements in the periodic table,
Ionic- non-metal and metal
Covalent- both non metals
Dative- if the shared pair of electrons come from the same atom

Strontium chloride- strontium is metal and chlorine is non-metal therefore it is ionic :smile:

Reply 317

Original post by haj101

You need to be able to identify the metal and non metal elements in the periodic table,
Ionic- non-metal and metal
Covalent- both non metals
Dative- if the shared pair of electrons come from the same atom

Strontium chloride- strontium is metal and chlorine is non-metal therefore it is ionic :smile:

thank you so much :smile:

Reply 318