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March 29, 2024, 12:19:31 pm

Author Topic: VCE Chemistry Question Thread  (Read 2313529 times)  Share 

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sweetcheeks

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Re: VCE Chemistry Question Thread
« Reply #5790 on: October 25, 2016, 09:09:45 am »
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Okay thanks,


I have a question about redox http://m.imgur.com/1vtP82x

I'm a bit confused for part b and c. Since both reactants are only solutions/ions, there won't be anything becoming a solid, so therefore no redox reactions occurs? Is this correct?

Thanks
A redox reaction is still occurring, there is nothing to state that a solid must be involved in someway for a reaction to occur. This video shows a reaction between MnO4- ions and H2O2: https://www.youtube.com/watch?v=OLUyeCC-2Ko
Another common reaction is the titration between Mno4- and Fe2+ ions. The purple MnO4- will be reduced by the Fe2+ ions which will be oxidised to Fe3+.

Adequace

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Re: VCE Chemistry Question Thread
« Reply #5791 on: October 25, 2016, 06:09:36 pm »
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A redox reaction is still occurring, there is nothing to state that a solid must be involved in someway for a reaction to occur. This video shows a reaction between MnO4- ions and H2O2: https://www.youtube.com/watch?v=OLUyeCC-2Ko
Another common reaction is the titration between Mno4- and Fe2+ ions. The purple MnO4- will be reduced by the Fe2+ ions which will be oxidised to Fe3+.
Thanks for consistently answering my chem questions sweetcheeks, much love!!!!

Edit: for Q2c) So KMnO4 and H2O2 causes a reaction? My teacher says it doesn't and the top-left, bottom-right rule isn't satisfied when I consider K+ ions with H2O2 on the electrochemical series?
« Last Edit: October 25, 2016, 06:24:44 pm by Adequace »

HopefulLawStudent

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Re: VCE Chemistry Question Thread
« Reply #5792 on: October 25, 2016, 07:21:39 pm »
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Does denaturation affect the tertiary and secondary structures or just the tertiary?

Elizawei

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Re: VCE Chemistry Question Thread
« Reply #5793 on: October 25, 2016, 08:50:17 pm »
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Does denaturation affect the tertiary and secondary structures or just the tertiary?

Affects both I'm pretty sure.The secondary structure is the formation of helices or sheets held together by hydrogen bonding, and denaturation by increasing temperature will certainly break these hydrogen bonds, disrupting the secondary structure as well as the tertiary. However last year for bio I think I've always talked about denaturation in regards to the tertiary structure, but I guess for chem it's more to do with the bonding :)
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sweetcheeks

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Re: VCE Chemistry Question Thread
« Reply #5794 on: October 25, 2016, 09:02:30 pm »
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Does denaturation affect the tertiary and secondary structures or just the tertiary?
pH denaturation affects tertiary structure (think of acidic/basic side chains)
Temperature affects both the secondary and tertiary.

Generally this question will be asked in the terms of an enzyme. The answer they generally look for is that the active site, which is part of the tertiary structure, is disrupted, resulting in an enzyme that no longer functions.

klippo

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Re: VCE Chemistry Question Thread
« Reply #5795 on: October 26, 2016, 09:47:11 pm »
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Hi guys, just wondering what strong/weak acids and strong/weak bases are we required to know? This is what I've got so far:

Strong acids - sulfuric acid, hydrochloric acid, nitric acid
Weak acids - ethanoic acid, ammonium
Strong bases - metal hydroxides
Weak bases - Ammonia

Thanks!

duling

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Re: VCE Chemistry Question Thread
« Reply #5796 on: October 27, 2016, 11:43:38 am »
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Hey Klippo

Thats all the strong acids you need to know :), with the weak acids you will find a list of all of them in your data book so you don't need to memorise them. I am not sure what you mean by 'metal hydroxides' being bases. The only strong base you need to know is NaOH (sodium hydroxide) and ammonia is pretty much the only weak base you need to know.

mayonnaise

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Re: VCE Chemistry Question Thread
« Reply #5797 on: October 29, 2016, 09:56:50 pm »
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How do I use this equation properly?

Energy kJ = (delta H / coefficient) x moles

Because if the coefficient of the thing is 2,
E.g. 2Mg + O2 >>> 2MgO
Delta H = -1200 kJ/mol

Do I have to times the delta H by 2? And then divide by the coefficient which is 2? to find the amount of energy released.
Because my teacher said it's not 'molar enthalpy' or something if I don't do that????
But that just seems really pointless.

So I got really confused from all this.
Does the 'coefficient' part of the above formula ever have a point?

Sorry if this question doesn't make sense  ;D

staceyschh

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Re: VCE Chemistry Question Thread
« Reply #5798 on: October 29, 2016, 11:53:29 pm »
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I have another question but about redox http://imgur.com/9TvtKk9

I'm trying to find out which thing is undergoing oxidation. For the first equation, I know that the F arrow is the oxidation equation but I tried finding the oxidation number of 2CuI to make sure I knew that this was undergoing reduction, but I'm stuck. I'm not sure what the oxidation number of I is, so can't solve for the oxidation number of Cu.

The 2nd equation, I'm just unsure how to do this so I kinda guessed. What do I do if theres 2 things that I don't know the oxidation numbers for? Those things being K and Cl that is in KClO?


Think of it like a number line. Whenever you gain electrons, the charge becomes more towards the negatives. When you lose electrons, the charge becomes more towards the positives. In most cases, oxidation numbers are the same as the ionic charge. but NOT always!!!


Oxidation is Loss, Reduction is Gain (OILRIG)

If I have an Oxidation state of +2, and I lose 1 electron, my charge becomes +3 because I have one less negative charge.

If I have an Oxidation state of +1 and I gain 2 electrons, my charge becomes -1 because I have more negative charges.

Essentially you can break these up into half equations and remember ORRL.

Oxidation Right
Reduction Left

These are the sides the electrons go on in the half equations.

not sure if this is helpful to you but yeah.

klippo

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Re: VCE Chemistry Question Thread
« Reply #5799 on: October 30, 2016, 11:29:50 am »
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Hi guys,

I'm just a little confused about cells. So primary cells are unrechargable and secondary are rechargeable.

I thought that galvanic cells were unrechargable, but there are secondary galvanic cells, so is that initial definition of galvanic cells incorrect?

Also are electrolytic cells secondary cells? Or are they something different? And what is the difference between an electrolytic cell and a secondary galvanic cell?

Thank you!

FutureDoctor2k16

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Re: VCE Chemistry Question Thread
« Reply #5800 on: October 31, 2016, 02:14:45 pm »
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For the dissolution of HCOOH, if we're asked to write the equation, how do we know if HCOOH is a liquid or aq???

rosecookiie

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Re: VCE Chemistry Question Thread
« Reply #5801 on: October 31, 2016, 02:27:01 pm »
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For the dissolution of HCOOH, if we're asked to write the equation, how do we know if HCOOH is a liquid or aq???


I think we write (aq) unless they state otherwise, but I'm not entirely sure
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sweetcheeks

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Re: VCE Chemistry Question Thread
« Reply #5802 on: October 31, 2016, 04:09:34 pm »
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For the dissolution of HCOOH, if we're asked to write the equation, how do we know if HCOOH is a liquid or aq???
Write it as aqueous. On the 2013 VCAA exam, they write it as aqueous. It is dissolved in water, therefore it is aqueous.

larissaaa_

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Re: VCE Chemistry Question Thread
« Reply #5803 on: October 31, 2016, 04:18:39 pm »
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This may be a bit late to ask but better now than never. Can someone tell me everything I need to know about significant figures and how to know how many sig figs we need when answering a particular question thank you

HopefulLawStudent

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Re: VCE Chemistry Question Thread
« Reply #5804 on: October 31, 2016, 05:13:13 pm »
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For the dissolution of HCOOH, if we're asked to write the equation, how do we know if HCOOH is a liquid or aq???

I think we write (aq) unless they state otherwise, but I'm not entirely sure
Write it as aqueous. On the 2013 VCAA exam, they write it as aqueous. It is dissolved in water, therefore it is aqueous.

Erm,,, Are you guys sure? I did the 2011 Exam 2 this morning and: HCOOH was a liquid.  ???

(Future2k16: Do you know the answer? Is it supposed to be a l or aq?!)