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2005 - Multiple choice - Q16,23,34,40 - HSN forum

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2005 - Multiple choice - Q16,23,34,40


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#1 Pyrefly

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Posted 22 May 2006 - 02:30 PM

I need help on the following qustions from the 2005 MC.

Q16
Approcimetely how many atoms will be present in 11.5 litres of carbon monoxide?
(take the molar volume of carbon monoxide to be 23 litres mil^-1)
A 1.5*10^23
B 3*10^23
C 6*10^23
D 1.2*10^23


Q23
Oxidation of 4-methylpent-2-ol useing copper(II) oxide results in the alcohol
A losing 2g per mole
B gaining 2g per mole
C gaining 16g per mole
D no change in mass

Q34
Cant really type out the equilibreum ones..
Cl2 (g) + H2O (l) <----> Cl- (aq) + 2H+ (aq)
hopefully whoever helps has this past paper to look at rather than trying to decifer my attempt at showing the equilibrium.....
anyway...
The addition of which of the following substances would move the above equilibrium to the right?
A Hydrogen
B Hydrogen Choloride
C Sodium Chloride
D Sodim hydroxide
(I think i understand this one now..but it would be good to see a smart persons answer tongue.gif)

Q40
This one is a graph one...so also cant type it out.


Thanks in advance smile.gif

#2 Nathan

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Posted 22 May 2006 - 02:42 PM

16. 11.5l = 0.5mole = 3x1023 molecules

1 mole = 6x1023 molecules = 12x1023 atoms

0.5 mole = 6x1023 ...answer C

34. hydrogen will shift to the left, HCl will also shift to the left, NaCl again to the left, leaving NaOH which will shift equilibrium to the right... answer D


#3 Michael

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Posted 22 May 2006 - 02:47 PM

Slight correction to the explanation of 34. Hydrogen will do nothing, it doesnt move to the left as its not H+.

HCl and NaCl will move both to the left. NaOH is an alkali and will therefore remove the H+ ions from solution so the equilibrium will shift to create more product(i.e. to the right).

#4 Pyrefly

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Posted 22 May 2006 - 02:53 PM

QUOTE(nathanm @ May 22 2006, 03:42 PM) View Post

16. 11.5l = 0.5mole = 3x1023 molecules

1 mole = 6x1023 molecules = 12x1023 atoms

0.5 mole = 6x1023 ...answer C

34. hydrogen will shift to the left, HCl will also shift to the left, NaCl again to the left, leaving NaOH which will shift equilibrium to the right... answer D


ahh....thats how it works....I 0.5 * 6(.02)*10^23...forgot that it 6(.02)*10^23 molecules which went to become 12*10^23 atoms

Thank you tongue.gif

just need help with the other two smile.gif

#5 Pammy

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Posted 22 May 2006 - 03:00 PM

For 16 I did

No. moles = Volume/ Molar vol.
= 11.5/23
= 0.5 moles

Then 0.5 * 6.02*10^3 = 3.01*10^23

which is answer B, but the answers say C, so I'm obviously doing it wrong !!
Could someone please pick holes in my working, and show me where I am going wrong ??


23

Molecular formula before oxidising = C base6.gif H base1.gif base4.gif O

Molecular formula after oxidising = C base6.gif H base1.gif base2.gif O

Therefore you lose two hydrogens, which equal 1g each, therefore total loss of 2g per mole

Answer: A


34

Addition of hydrogen would move position to the left as you would be adding to the 2H+

Addition of HCL would move position to the left as you would be adding to the Cl-

Addition of Sodium Chloride would move position to the left as you would be adding to the Cl-

Addition of Sodium Hydroxide would move position to the right as the OH- will combine with the 2H+ to form water, hence removing a product.

Answer: D

Hope that helps !!!!

Edit: By the time I wrote all that out lots of people had beaten me to it, and it's ok, I now see my error in Q 16
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

#6 Michael

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Posted 22 May 2006 - 03:00 PM

Adding hydrogen is completely different to adding H+

#7 Nathan

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Posted 22 May 2006 - 03:02 PM

i really don't get Q40...there was something similar in my supp. prelim and i didn't understand it then rolleyes.gif

#8 Pyrefly

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Posted 22 May 2006 - 03:14 PM

QUOTE(nathanm @ May 22 2006, 04:02 PM) View Post

i really don't get Q40...there was something similar in my supp. prelim and i didn't understand it then rolleyes.gif



ya i had the same kind of question in my support prelum too...but that time i guessed the right answer...i really dont understand it...

Does anyone have a link to where i can find the definitions of each of the different things liek oxidation, condensation, hydrolosis....theres so many now im getting a little confused.

I remeber in standard grade learning LEO and REG

Losing electrons = oxidation
Reduction= electron gain

or was it something else....im a tad confused with Chemistry tongue.gif

also anyone had any idea about Q 40?

#9 eyecandy

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Posted 22 May 2006 - 03:19 PM

its.....

Oxidation
Is
Loss
Reduction
Is
Gain

#10 Pammy

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Posted 22 May 2006 - 03:21 PM

Ta Da !!!!!!!!!!!!!!!!!!! Don't know if this is what you wanted, but it's
pretty good anyway !!

Reactions[u]

Condensation: Molecules combine, releasing a small molecule (usually water) at each join. For example, when acids and alcohols form esters and when amino acids form proteins.

Hydrolysis: The opposite of condensation. A larger molecule breaks apart as water is added to it. For example, when an ester breaks down to acid and alcohol.

Oxidation: Addition of oxygen or removal of hydrogen, decreasing the ratio of oxygen to hydrogen in a compound.

Addition: Double or triple bonds open up and bond to other atoms. A double bond adds one mole of a compound e.g bromine. A triple bond adds two moles of a compound.

Hydrogenation: Addition of hydrogen.

Dehydrogenation: Removal of hydrogen.

Hydration: This is addition of water to the double bond, as an H to one atom and an OH to another. It can be used to convert an alkene to an alcohol.

Dehydration: The opposite of hydration, often catalysed by aluminium oxide. Actual products depend on where the double bond is located in the molecule.

Addition Polymerisation: This type of polymerisation results from addition of molecules across double bonds. It can only occur when the monomer has a C=C double bond.

Condensation Polymerisation: This type of polymerisation occurs when monomers have two functional groups, enabling the condensation reactions to take place at each end of the molecule.

Cracking: This involves long chain alkanes being broken down into shorter alkanes and alkenes. Heat and a catalyst (aluminium oxide) are often required.

Reforming: This is really a set of reactions, which rearrange the atoms in an organic molecule, without greatly altering the number of carbon atoms.

*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

#11 Pyrefly

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Posted 22 May 2006 - 03:22 PM

Thats great! thanks alot biggrin.gif

#12 Nathan

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Posted 22 May 2006 - 03:23 PM

QUOTE(Pyrefly @ May 22 2006, 04:14 PM) View Post

Does anyone have a link to where i can find the definitions of each of the different things liek oxidation, condensation, hydrolosis....theres so many now im getting a little confused.


have a wee look at the HSN chemistry notes: http://www.hsn.uk.net/resources/Higher-Chemistry

most of the stuff you mentioned comes up in unit two

edit: or not rolleyes.gif

#13 Pammy

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Posted 22 May 2006 - 03:26 PM

* tumbleweed blows in the wind *

No-one sure about Q40 then ?? rolleyes.gif
It's starting to annoy me mad.gif
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

#14 Pyrefly

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Posted 22 May 2006 - 03:34 PM

QUOTE(Pammy @ May 22 2006, 04:26 PM) View Post

* tumbleweed blows in the wind *

No-one sure about Q40 then ?? rolleyes.gif
It's starting to annoy me mad.gif



lol.. *takes out calculator and starts pressing random numbers*

hmm....

#15 Nathan

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Posted 22 May 2006 - 03:35 PM

QUOTE(Pyrefly @ May 22 2006, 04:34 PM) View Post

QUOTE(Pammy @ May 22 2006, 04:26 PM) View Post

* tumbleweed blows in the wind *

No-one sure about Q40 then ?? rolleyes.gif
It's starting to annoy me mad.gif



lol.. *takes out calculator and starts pressing random numbers*

hmm....


laugh.gif

what is the answer meant to be blink.gif

#16 Pammy

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Posted 22 May 2006 - 03:35 PM

If no-one gets it I'm gonna have to go with my coincidental answer of
'well 4 days is half of 8 days'
laugh.gif rolleyes.gif biggrin.gif blink.gif
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

#17 Pyrefly

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Posted 22 May 2006 - 03:36 PM

Lets see....im gonna ignore the first line on the graph..since it confuses me tongue.gif

The second one is at 25% which is 2 half lifes. And The sample is 8 days old. that means that the half life is 4 days.

only thing that confuses me is what the first line is there for...just to look confusing?

#18 Nathan

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Posted 22 May 2006 - 03:40 PM

QUOTE(Pyrefly @ May 22 2006, 04:36 PM) View Post

Lets see....im gonna ignore the first line on the graph..since it confuses me tongue.gif

The second one is at 25% which is 2 half lifes. And The sample is 8 days old. that means that the half life is 4 days.

only thing that confuses me is what the first line is there for...just to look confusing?


maybe the first one isn't as radioactive unsure.gif rolleyes.gif

#19 Pammy

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Posted 22 May 2006 - 03:41 PM

QUOTE(Pyrefly @ May 22 2006, 03:36 PM) View Post

Lets see....im gonna ignore the first line on the graph..since it confuses me tongue.gif


haha lol i like u !!! U think like me biggrin.gif
And maybe you are right !!! It's better than my '4 is half of 8' theory
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

#20 Pyrefly

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Posted 22 May 2006 - 03:58 PM

QUOTE(Pammy @ May 22 2006, 04:41 PM) View Post

QUOTE(Pyrefly @ May 22 2006, 03:36 PM) View Post

Lets see....im gonna ignore the first line on the graph..since it confuses me tongue.gif


haha lol i like u !!! U think like me biggrin.gif
And maybe you are right !!! It's better than my '4 is half of 8' theory



lol thats just how these kinda things work...just like the theory of when your stuck at other multi choice....It must be an A! as there hasn't been an A in ageeess tongue.gif

OH!!! I GET IT!

there is 75% on the first graph which is the amount that has been lost!
there is 25% on the second graph the amount that is left!

so...the 25% is 2 half lifes. And 8 days devided by the 2 half lifes means the half life is 4days

(basically you can ignore the first one....its just what has been lost...i think)





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