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November 01, 2025, 11:55:00 am
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Author Topic: Interesting questions (chem)  (Read 7260 times)  Share 

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fady_22

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Re: Interesting questions (chem)
« Reply #45 on: November 07, 2010, 10:15:22 pm »
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Quote from: m@tty on November 07, 2010, 10:07:16 pm
Oh yeah, ok.



So initial

Final

So you need 0.1 M to neutralise and 0.1 M to make the pH right.

?? ..
At the risk of sounding stupid: 
You are adding 1 mole of acid to a larger volume of water (after neutralisation). It would dilute the acid, increasing the pH. Don't you need to account for this?
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Martoman

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Re: Interesting questions (chem)
« Reply #46 on: November 07, 2010, 10:16:25 pm »
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well its nice, not immediately obvious.

I apologize for not overwhelming you with quantum entanglement or the fundamental theory of algebra  :smitten:


Quote from: fady_22 on November 07, 2010, 10:15:22 pm
Quote from: m@tty on November 07, 2010, 10:07:16 pm
Oh yeah, ok.



So initial

Final

So you need 0.1 M to neutralise and 0.1 M to make the pH right.

?? ..
At the risk of sounding stupid:  
You are adding 1 mole of acid to a larger volume of water (after neutralisation). It would dilute the acid, increasing the pH. Don't you need to account for this?

*you do* but this is VCE chemsitry. (refer to 2007 exam 1 MC Q 16)
« Last Edit: November 07, 2010, 10:21:07 pm by Martoman »
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m@tty

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Re: Interesting questions (chem)
« Reply #47 on: November 07, 2010, 10:19:26 pm »
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Apology accepted.

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fady_22

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Re: Interesting questions (chem)
« Reply #48 on: November 07, 2010, 10:20:20 pm »
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Stupid VCE.  :)
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m@tty

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Re: Interesting questions (chem)
« Reply #49 on: November 07, 2010, 10:22:03 pm »
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If we had to account for dilution it would result in an "unsolvable" DE (using Spec methods). Just like the 'changing volume' mixing problems from Spec.

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Martoman

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Re: Interesting questions (chem)
« Reply #50 on: November 07, 2010, 10:22:42 pm »
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I was gonna say you CAN solve a diff equation with multivariable....
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fady_22

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Re: Interesting questions (chem)
« Reply #51 on: November 07, 2010, 10:23:12 pm »
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Quote from: m@tty on November 07, 2010, 10:22:03 pm
If we had to account for dilution it would result in an "unsolvable" DE (using Spec methods).

But still solvable outside the world of VCE maths.
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Re: Interesting questions (chem)
« Reply #52 on: November 07, 2010, 10:23:52 pm »
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Yeah we did one in MUEP...

Derrick Ha said that they were unsolvable *even* using uni methods.  :idiot2:
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Martoman

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Re: Interesting questions (chem)
« Reply #53 on: November 07, 2010, 10:24:18 pm »
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HA he's wrong  :angel:
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fady_22

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Re: Interesting questions (chem)
« Reply #54 on: November 07, 2010, 10:33:15 pm »
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Quote from: Martoman on November 07, 2010, 10:16:25 pm
*you do* but this is VCE chemsitry. (refer to 2007 exam 1 MC Q 16)

That question is different. The volume remains constant (as you are adding HCl gas).
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Re: Interesting questions (chem)
« Reply #55 on: November 07, 2010, 10:41:13 pm »
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you add gas the gas must go aqueous.
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Mao

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Re: Interesting questions (chem)
« Reply #56 on: November 07, 2010, 10:42:15 pm »
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How about this:

What volume of 1M HNO3 would be required to bring 1L of NaOH at pH=13 to pH=1? (answer: 2/9 L)
« Last Edit: November 07, 2010, 10:44:14 pm by Mao »
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fady_22

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Re: Interesting questions (chem)
« Reply #57 on: November 07, 2010, 10:47:03 pm »
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222 mL?







« Last Edit: November 07, 2010, 10:50:23 pm by fady_22 »
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Re: Interesting questions (chem)
« Reply #58 on: November 07, 2010, 10:47:57 pm »
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Quote from: fady_22 on November 07, 2010, 10:47:03 pm
222 mL?
If it's right, I'll show my working.

=)
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Martoman

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Re: Interesting questions (chem)
« Reply #59 on: November 08, 2010, 07:23:06 pm »
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Explain why electrolysing a dilute solution of sodium chloride is more efficient in producing hydrogen than just electrolysing pure water.
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