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October 12, 2025, 09:09:07 am
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Author Topic: HSC Chemistry Question Thread  (Read 1292909 times)  Share 

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Mate2425

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Re: Chemistry Question Thread
« Reply #3360 on: March 20, 2018, 11:48:13 am »
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Quote from: kiwiberry on March 20, 2018, 03:45:30 am
Yep :)

The image isn’t appearing for me!!
Thank you
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3.14159265359

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Re: Chemistry Question Thread
« Reply #3361 on: March 20, 2018, 06:28:01 pm »
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Quote from: kiwiberry on March 20, 2018, 03:45:30 am

The image isn’t appearing for me!!

is there a way to post the picture. its not letting me send it. I tried everything
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RuiAce

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Re: Chemistry Question Thread
« Reply #3362 on: March 20, 2018, 06:32:28 pm »
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Quote from: 3.14159265359 on March 20, 2018, 06:28:01 pm
is there a way to post the picture. its not letting me send it. I tried everything
Looking at your attachment you posted an image file that's 0kb, which would imply that it's a blank image. So potentially the forum is messing up but some problem is existing between your image and the servers.

The alternative is to upload it to imgur and then manually link it.
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3.14159265359

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Re: Chemistry Question Thread
« Reply #3363 on: March 20, 2018, 06:34:24 pm »
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oh wait I got it
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RuiAce

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Re: Chemistry Question Thread
« Reply #3364 on: March 20, 2018, 06:37:11 pm »
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Quote from: 3.14159265359 on March 20, 2018, 06:34:24 pm
oh wait I got it
Is there something missing (or in an earlier part)? You subbed 0.25L in for \(V_2\) but I don't know why
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3.14159265359

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Re: Chemistry Question Thread
« Reply #3365 on: March 20, 2018, 06:40:10 pm »
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Quote from: RuiAce on March 20, 2018, 06:37:11 pm
Is there something missing (or in an earlier part)? You subbed 0.25L in for \(V_2\) but I don't know why

oh because I was going to prepare that in a 250 ml volumetric flask
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RuiAce

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Re: Chemistry Question Thread
« Reply #3366 on: March 20, 2018, 06:42:56 pm »
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Quote from: 3.14159265359 on March 20, 2018, 06:40:10 pm
oh because I was going to prepare that in a 250 ml volumetric flask
In that case,

As you correctly calculated, you should have 2.5 mL of HCl at the start. Using the dilutions formula, the combined volume of everything at the end will be 250 mL.

Therefore, you need to add \( 250 - 2.5 = 247.5\text{ mL}\) of water.
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LaraC

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Re: Chemistry Question Thread
« Reply #3367 on: March 20, 2018, 06:56:27 pm »
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Hello, can someone please help me out with this question?

The salt, potassium hydrogen carbonate (KHCO3) hydrolyses in water to produce a basic solution. Write a balanced equation to explain why the solution is basic.
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3.14159265359

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Re: Chemistry Question Thread
« Reply #3368 on: March 20, 2018, 06:57:40 pm »
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Quote from: RuiAce on March 20, 2018, 06:42:56 pm
In that case,

As you correctly calculated, you should have 2.5 mL of HCl at the start. Using the dilutions formula, the combined volume of everything at the end will be 250 mL.

Therefore, you need to add \( 250 - 2.5 = 247.5\text{ mL}\) of water.

am I supposed to do a method explaining what to do? like how to perform a hcl standard? or something along those lines? but the thing is hcl can't be a standard because it doesn't meet the criteria.
btw this was the marking guidelines for it
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3.14159265359

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Re: Chemistry Question Thread
« Reply #3369 on: March 20, 2018, 07:02:46 pm »
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Quote from: LaraC on March 20, 2018, 06:56:27 pm
Hello, can someone please help me out with this question?

The salt, potassium hydrogen carbonate (KHCO3) hydrolyses in water to produce a basic solution. Write a balanced equation to explain why the solution is basic.


hco3^- +h2o <--> h2co3 +oh^-

the solution is basic as hydroxide was produced which is an indication of a base present. also when you write the equation you disregard the potassium (k) because its a neutral as it doesn't react with water because it comes from the strong base KOH
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RuiAce

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Re: Chemistry Question Thread
« Reply #3370 on: March 21, 2018, 07:09:50 pm »
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Quote from: 3.14159265359 on March 20, 2018, 06:57:40 pm
am I supposed to do a method explaining what to do? like how to perform a hcl standard? or something along those lines? but the thing is hcl can't be a standard because it doesn't meet the criteria.
btw this was the marking guidelines for it
At first glance, the marking guidelines given don't mention anything about 250 mL HCl at the start.

If anything, I'd use titration against something like anhydrous \(Na_2CO_3\) instead. HCl certainly cannot be a primary standard, but I see no problem with it being a secondary standard.
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LaraC

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Re: Chemistry Question Thread
« Reply #3371 on: March 23, 2018, 12:03:58 pm »
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Qu: is a solution made using equal volumes of sulfuric acid and sodium sulfate a buffer solution and why?

Also, I'm not sure if there is such a thing as a brief rundown/explanation on titrations, but if there is, would anyone please mind helping me out? I'm pretty confused by the whole deal! Thanks :)
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LaraC

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Re: Chemistry Question Thread
« Reply #3372 on: March 24, 2018, 09:39:00 pm »
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Maybe I'll try with a different question ;)
I'm really stuck with this and if someone could possibly help me that would be awesome!! :D

The sulfate concentration in a sample of water can be determined gravimetrically by:
- first adding acid to the sample to react with carbonate ions
- then adding excess barium ions
- filtering off, drying and weighing the BaSO4 precipitate formed.

Barium carbonate is insoluble. Adding acid before adding barium ions prevents BaCO3 precipitating with the BaSO4. Write a balanced equation for the reaction in which H+ ions destroy a carbonate ion releasing a gas.

Thanks so much!!
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fireives1967

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Re: Chemistry Question Thread
« Reply #3373 on: March 24, 2018, 11:02:26 pm »
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What is a valid equation to explain addition polymerisation?

I've tried to use Ethene(s) monomers --> Polyethylene through

n(C2H4) --> (C2H4)n but I'm not sure if it's quite correct.

Can someone please provide a valid equation????

Much appreciated!!!!  ;D
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beeangkah

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Re: Chemistry Question Thread
« Reply #3374 on: March 25, 2018, 08:46:36 am »
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Hi, just a quick question on graphing.

If the question does not specify, do we draw a line of best fit or join the dots? I've gotten mixed messages across the years so I'm not entirely sure.
And also same with curves of best fit.

Thanks!
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