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November 01, 2025, 11:32:16 am
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Author Topic: ssNake's Chemistry [u2] Q's  (Read 37829 times)  Share 

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Re: ssNake's Chemistry [u2] Q's
« Reply #150 on: October 11, 2011, 07:22:17 pm »
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Quote from: ssNake on October 09, 2011, 12:50:22 pm
Classify this reaction: HCN + H20 -----> CN- + H3O+

I said 'acid-base'

Checkpts says 'ionisation'

They're both right?
^ anyone?
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Re: ssNake's Chemistry [u2] Q's
« Reply #151 on: October 11, 2011, 07:52:22 pm »
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Yeah i think they're both right, but ionisation would be more correct cos its ionising in the presence of water.
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Re: ssNake's Chemistry [u2] Q's
« Reply #152 on: October 13, 2011, 05:07:16 pm »
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X + 2H2O ---> X(OH)2 + H2

X could represent the element:

a) iron
b) calcium
c) sulphur
d) copper

Rule out C obviously. How to differ b/w a,b and c?
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Re: ssNake's Chemistry [u2] Q's
« Reply #153 on: October 13, 2011, 05:19:02 pm »
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Think redox
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Re: ssNake's Chemistry [u2] Q's
« Reply #154 on: October 13, 2011, 05:21:27 pm »
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X has been oxidised...?

But Fe --> Fe2+    Ca ---> Ca2+    Cu ---> Cu2+

Can't it be either?
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Re: ssNake's Chemistry [u2] Q's
« Reply #155 on: October 13, 2011, 05:22:37 pm »
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Quote from: ssNake on October 13, 2011, 05:21:27 pm
X has been oxidised...?

But Fe --> Fe2+    Ca ---> Ca2+    Cu ---> Cu2+

Can't it be either?

now think electrochemical series.
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Re: ssNake's Chemistry [u2] Q's
« Reply #156 on: October 13, 2011, 05:23:35 pm »
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Ca is the strongest reductant so it's Ca?
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Re: ssNake's Chemistry [u2] Q's
« Reply #157 on: October 13, 2011, 05:47:32 pm »
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Quote from: ssNake on October 13, 2011, 05:23:35 pm
Ca is the strongest reductant so it's Ca?

Yes, X is Ca as it is below H20 on the electrochemical series (hence, "negative gradient" for a spontaneous reaction is established)
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Re: ssNake's Chemistry [u2] Q's
« Reply #158 on: October 13, 2011, 05:49:22 pm »
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Well the answer was Iron....

-.-
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Re: ssNake's Chemistry [u2] Q's
« Reply #159 on: October 13, 2011, 07:01:06 pm »
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Quote from: ssNake on October 13, 2011, 05:49:22 pm
Well the answer was Iron....

-.-

It's wrong afaik
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Re: ssNake's Chemistry [u2] Q's
« Reply #160 on: October 14, 2011, 01:29:42 am »
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Quote from: pi on October 13, 2011, 07:01:06 pm
Quote from: ssNake on October 13, 2011, 05:49:22 pm
Well the answer was Iron....

-.-

It's wrong afaik

Agreed.

Moderator action: removed real name, sorry for the inconvenience
« Last Edit: January 15, 2017, 05:00:56 pm by pi »
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Re: ssNake's Chemistry [u2] Q's
« Reply #161 on: October 15, 2011, 11:02:42 am »
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Split this into two half-eqs

VO2+ + H20 + ClO4-      ----> V(OH)4+ + H+ + Cl-

I can do the reduction of ClO4- ----> Cl-

however the VO2+ ---> V(OH)4+ isn't working out.
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Re: ssNake's Chemistry [u2] Q's
« Reply #162 on: October 15, 2011, 11:51:41 am »
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Quote from: ssNake on October 15, 2011, 11:02:42 am
Split this into two half-eqs

VO2+ + H20 + ClO4-      ----> V(OH)4+ + H+ + Cl-

I can do the reduction of ClO4- ----> Cl-

however the VO2+ ---> V(OH)4+ isn't working out.

VO2+ ---> V(OH)4+
VO2+ + 3H2O ---> V(OH)4+
VO2+ + 3H2O ---> V(OH)4+ + 2H+
VO2+ + 3H2O ---> V(OH)4+ + 2H+ + e-

Seems right

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Re: ssNake's Chemistry [u2] Q's
« Reply #163 on: October 15, 2011, 11:52:57 am »
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2nd step ---> why'd you put 3H2O when the right hand side only has 4H+ from the (OH)4

wouldn't you put 2H2O?
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Re: ssNake's Chemistry [u2] Q's
« Reply #164 on: October 15, 2011, 11:54:46 am »
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Quote from: ssNake on October 15, 2011, 11:52:57 am
2nd step ---> why'd you put 3H2O when the right hand side only has 4H+ from the (OH)4

wouldn't you put 2H2O?

You always balance O before you balance H

edit: note that there was already one O on the LHS, hence I added 3H2O to balance the O
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