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May 16, 2022, 03:23:10 pm

Author Topic: VCE Chemistry Question Thread  (Read 1944154 times)  Share 

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user28

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Re: VCE Chemistry Question Thread
« Reply #9255 on: January 26, 2022, 11:54:42 pm »
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I need help with a question!

a)What mass of iron may be extracted from 1000 tonnes of Fe3O4 according to
3Fe3O4(s)+8Al(s)-->4Al2O3(s)+9Fe(s)?

b) What mass of aluminium is used in the process?

All help would be appreciated. Thanks!  :) :)

Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9256 on: January 27, 2022, 12:55:42 am »
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I need help with a question!

a)What mass of iron may be extracted from 1000 tonnes of Fe3O4 according to
3Fe3O4(s)+8Al(s)-->4Al2O3(s)+9Fe(s)?

b) What mass of aluminium is used in the process?

All help would be appreciated. Thanks!  :) :)

a) 1000 t = 1000 kg = 1000000 g
n(Fe3O4) = 1000000 g / 231.533 g/mol = 4319.0387547... mol
n(Fe) = 3 x n(Fe3O4)
m(Fe) = (3 x 4319.0387547... mol) x 55.845 g/mol x 1/1000 kg/g = 723.6 kg to 4 sig figs

b) n(Al) = (8/3) x n(Fe3O4)
m(Al) = (8/3) x 4319.0387547... mol x 26.98 g/mol x 1/1000 kg/g = 310.7 kg to 4 sig figs

Note that you can check if your calculations are correct or not with dimensional analysis, all units will cancel to the appropriate unit of the final answer if you did everything correctly. For example, mol cancels out mol-1 or /mol and g cancels out g-1 or /g etc
« Last Edit: January 27, 2022, 12:58:35 am by Billuminati »
VCE 2016-2018

2017: Biology [38], Further Maths [44]

2018: Methods [37], French [38], Chem [40], English [44]

UMAT: 56/43/80, 57th percentile (LLLLOOOOOOOOOLLLLLLLL)

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2019- : Bachelor of Biomedical Science at Monash (Scholars), minoring in Chemistry

GAMSAT September 2021: 65/67/86, 76 overall (98th percentile)

user28

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Re: VCE Chemistry Question Thread
« Reply #9257 on: January 27, 2022, 12:38:43 pm »
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a) 1000 t = 1000 kg = 1000000 g
n(Fe3O4) = 1000000 g / 231.533 g/mol = 4319.0387547... mol
n(Fe) = 3 x n(Fe3O4)
m(Fe) = (3 x 4319.0387547... mol) x 55.845 g/mol x 1/1000 kg/g = 723.6 kg to 4 sig figs

b) n(Al) = (8/3) x n(Fe3O4)
m(Al) = (8/3) x 4319.0387547... mol x 26.98 g/mol x 1/1000 kg/g = 310.7 kg to 4 sig figs

Note that you can check if your calculations are correct or not with dimensional analysis, all units will cancel to the appropriate unit of the final answer if you did everything correctly. For example, mol cancels out mol-1 or /mol and g cancels out g-1 or /g etc


Thank you v much:)

beep boop

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Re: VCE Chemistry Question Thread
« Reply #9258 on: January 27, 2022, 12:54:27 pm »
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I think this exact question appeared in my own chem exam (2018), I feel old now lol. Anyways, here are my workings: https://drive.google.com/file/d/1DL6s-0-drILAQL8-Zktp10xt12_k1Uky/view?usp=sharing

Hey Bill!

Thanks for your explanation. I don't think you're old ahaha.
 
beep boop
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lemurbruv

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Re: VCE Chemistry Question Thread
« Reply #9259 on: February 02, 2022, 09:05:34 pm »
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Hey all!

Does anyone know what the VCAA requirement is for the state you must write for H2O in equations? My teacher told me it should always be liquid, however due to credibility issues, I want to double-check. I've heard that my teacher could be wrong, so any advice/knowledge would be very much appreciated!!

Lemur
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ArtyDreams

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Re: VCE Chemistry Question Thread
« Reply #9260 on: February 02, 2022, 09:08:21 pm »
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Hey all!

Does anyone know what the VCAA requirement is for the state you must write for H2O in equations? My teacher told me it should always be liquid, however due to credibility issues, I want to double-check. I've heard that my teacher could be wrong, so any advice/knowledge would be very much appreciated!!

Lemur

Its liquid for all equations!
Except for combustion. It is better to write liquid and stay consistent but they do allow water written in gas state for combustion.

Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9261 on: February 02, 2022, 09:12:24 pm »
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Hey all!

Does anyone know what the VCAA requirement is for the state you must write for H2O in equations? My teacher told me it should always be liquid, however due to credibility issues, I want to double-check. I've heard that my teacher could be wrong, so any advice/knowledge would be very much appreciated!!
Lemur

Just answered you on the other thread, but according to my VCE chem teacher who was also a VCAA assessors, H2O should always be gas in combustion reactions UNLESS the question stem explicitly mentions "at standard conditions" or "at SLC", in which case it's liquid.

Also, VCAA thinks H2O(g) is a greenhouse gas associated with fossil fuel use, so this implies state of H2O should be (g)
« Last Edit: February 02, 2022, 09:16:12 pm by Billuminati »
VCE 2016-2018

2017: Biology [38], Further Maths [44]

2018: Methods [37], French [38], Chem [40], English [44]

UMAT: 56/43/80, 57th percentile (LLLLOOOOOOOOOLLLLLLLL)

ATAR: 98.1

2019- : Bachelor of Biomedical Science at Monash (Scholars), minoring in Chemistry

GAMSAT September 2021: 65/67/86, 76 overall (98th percentile)

lemurbruv

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Re: VCE Chemistry Question Thread
« Reply #9262 on: February 02, 2022, 09:15:49 pm »
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Just answered you on the other thread, but according to my VCE chem teacher who was also a VCAA assessors, H2O should always be gas in combustion reactions UNLESS the question stem explicitly mentions "at standard conditions" or "at SLC", in which case it's liquid
Its liquid for all equations!
Except for combustion. It is better to write liquid and stay consistent but they do allow water written in gas state for combustion.

Thanks so much for your help guys!!
class of 2022!
my year 12 VCE journal :)
2021: music
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biology1234

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Re: VCE Chemistry Question Thread
« Reply #9263 on: February 15, 2022, 06:43:05 pm »
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which non metal would be more reactive Nitrogen or Chloride using the periodic table to explain answer.
Would the answer be Nitrogen because nonmetals increase as they go up periodic table. Thanks

Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9264 on: February 15, 2022, 07:36:19 pm »
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which non metal would be more reactive Nitrogen or Chloride using the periodic table to explain answer.
Would the answer be Nitrogen because nonmetals increase as they go up periodic table. Thanks

Hint 1: Cl2 was used as a chemical weapon in WWI, whereas Earth’s atmosphere is 78% by partial pressure N2. Which gas do you think is more reactive given this?

Hint 2: Which of N2 or Cl2 is closer to the extreme left side (very electropositive) or extreme right side (very electronegative) of the periodic table and hence are more likely to give or take e-s respectively?
VCE 2016-2018

2017: Biology [38], Further Maths [44]

2018: Methods [37], French [38], Chem [40], English [44]

UMAT: 56/43/80, 57th percentile (LLLLOOOOOOOOOLLLLLLLL)

ATAR: 98.1

2019- : Bachelor of Biomedical Science at Monash (Scholars), minoring in Chemistry

GAMSAT September 2021: 65/67/86, 76 overall (98th percentile)

Rose34

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Re: VCE Chemistry Question Thread
« Reply #9265 on: February 16, 2022, 07:15:48 am »
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Hey,

Can someone please check this question? I have done it but not sure if I am right.. Please see attached

Thanks in advance.

Golgi Apparatus

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Re: VCE Chemistry Question Thread
« Reply #9266 on: February 16, 2022, 01:51:46 pm »
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Hey,

Can someone please check this question? I have done it but not sure if I am right.. Please see attached

Thanks in advance.

I think the delta H value given needs to be doubled instead of halved, as the coefficient of octane in the equation is two.

The delta H value in the equation should be this doubled value instead of 5460 kJ/mol, as delta H changes based on the coefficients in the equation. It should also have a negative sign, as combustion is exothermic and releases energy.

Apart from that, your working out seems correct :)
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biology1234

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Re: VCE Chemistry Question Thread
« Reply #9267 on: February 16, 2022, 06:16:06 pm »
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what would the electron configuration be for K +, potassium. I got this, 1s2 2s2 2p6 3s2 3p6 4s1. My answer book got 1s2 2s2 2p6 3p6. Would it not loose an electron as potassium is in group 1, and only need 18 electrons. Could someone explain

Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9268 on: February 16, 2022, 08:06:10 pm »
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what would the electron configuration be for K +, potassium. I got this, 1s2 2s2 2p6 3s2 3p6 4s1. My answer book got 1s2 2s2 2p6 3p6. Would it not loose an electron as potassium is in group 1, and only need 18 electrons. Could someone explain

Your answer is correct only for a neutral K atom (19 protons balanced by 19 e-s). For a K+ ion, it will lose one e- from the 4s orbital, so it only has 18 e-s
VCE 2016-2018

2017: Biology [38], Further Maths [44]

2018: Methods [37], French [38], Chem [40], English [44]

UMAT: 56/43/80, 57th percentile (LLLLOOOOOOOOOLLLLLLLL)

ATAR: 98.1

2019- : Bachelor of Biomedical Science at Monash (Scholars), minoring in Chemistry

GAMSAT September 2021: 65/67/86, 76 overall (98th percentile)

Chocolatepistachio

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Re: VCE Chemistry Question Thread
« Reply #9269 on: February 17, 2022, 02:11:20 pm »
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Which of the following statements about atp synthase is correct?
A atp synthase is located in the inner membrane of the mitochondrion
B atp synthase is located in the cytosol
C atp synthase is involved in glycolysis
D atp synthase is involved in electron transfer

Is this a but would d also be correct