***2013 LC Chemistry Before/After***

Jackobyte

0mega wrote: »

Same here but should it have been -57.96 for heat of reaction as it was exothermic and produced heat?

Yeah, I made mine negative as well.

@OulDublinHead: Averaging the temps at start was right.

ahmdoda

0mega wrote: »

Same here but should it have been -57.96 for heat of reaction as it was exothermic and produced heat?

flip forgot to include the minus argggggg!!!!!!!!!! hopefully wont loose much dumbass benzoic acid came up so couldnt do q2 so i was forced into 1 and 3

Jackobyte

Jackobyte wrote: »

Yeah, I made mine negative as well.

@OulDublinHead: Averaging the temps at start was right.

Thanks but then the initial temp was 14 and it reached 20.9 so should the heat change not be 6.9? Not around 4?

Glee_GG

Why don't we like air bubbles being trapped in the bottle for Q1?

_LilyRose_

For anyone who did Q8, did ye get UV light, HCl and Cl2 for part (b)? And what did you say for the reaction for conversion X?

simons545

Deleted User wrote: »

Thanks but then the initial temp was 14 and it reached 20.9 so should the heat change not be 6.9? Not around 4?

yep heat change was 6.9

xJEx

ladymacbeth wrote: »

So should it have been 1:4?
Or 2:1 as was suggested in the equation?

2:1 wasn't suggested in the equation for the oxygen??

Glee_GG

Glee_GG wrote: »

Why don't we like air bubbles being trapped in the bottle for Q1?

Because atmospheric O2 will dissolve into the sample and give an unusually high reading for dissolved O2.

_LilyRose_ wrote: »

For anyone who did Q8, did ye get UV light, HCl and Cl2 for part (b)? And what did you say for the reaction for conversion X?

Yup. And it was an ionic addition reaction

xJEx

Deleted User wrote: »

Sorry I just saw someone mention ammonia production.

For what speeds up rate of reaction.

1. Nature of reactants (are they both ionic or covalent) didn't apply to question
2. Temperature of reaction
3. Concentration of reactants
4. Particle size didn't apply
5. Presence of a catalyst

Oh never thought of catayst!! So would it be okay that I said increased temperature speeds up the rate even though it said the reaction was for ''the production of ammonia'' whose yield is decreased by temp?

_LilyRose_

xJEx wrote: »

2:1 wasn't suggested in the equation for the oxygen??

2S2O3 + I2 was written on the paper I think she means

Glee_GG

Deleted User wrote: »

Because atmospheric O2 will dissolve into the sample and give an unusually high reading for dissolved O2.

Ah ok, i had no idea so I just said you'd be adding extra oxygen to the mixture and it would effect results so thats grand out!

_LilyRose_

Deleted User wrote: »

Yup. And it was an ionic addition reaction

Yes! That question 8 terrified me but I made myself do it because I love that organic question!

Jackobyte

Deleted User wrote: »

Thanks but then the initial temp was 14 and it reached 20.9 so should the heat change not be 6.9? Not around 4?

Temperature change is 6.9, which is different to heat change. Heat change is found using:

ΔH=mcΔθ where m is mass, c is heat capacity and Δθ is temp change.

xJEx

xJEx wrote: »

Oh never thought of catayst!! So would it be okay that I said increased temperature speeds up the rate even though it said the reaction was for ''the production of ammonia'' whose yield is decreased by temp?

Yes. A high temperature has to be used to ensure a decent amount of effective collisions. Pressure however would be wrong as pressure affects equilibrium and not rate of reaction.

eoinoc2509

I thought that was horrible! Was i the only one?:(

xJEx

Deleted User wrote: »

Because atmospheric O2 will dissolve into the sample and give an unusually high reading for dissolved O2.

I said since we are calculating dissolved oxygen air bubbles containing oxygen would affect our result.
Would that get me the marks??

xJEx

Jackobyte wrote: »

Yeah, I made mine negative as well.

@OulDublinHead: Averaging the temps at start was right.

Damn i didnt do the negative sign, how many marks would i lose for that?

And so was it 0.075 moles then?

xJEx

xJEx wrote: »

I said since we are calculating dissolved oxygen air bubbles containing oxygen would affect our result.
Would that get me the marks??

If they are being ruthless with the marking scheme, I don't think it will. It all depends on the marking scheme though.

ahmdoda

_LilyRose_ wrote: »

For anyone who did Q8, did ye get UV light, HCl and Cl2 for part (b)? And what did you say for the reaction for conversion X?

i was going to write uv light but i wondered how is uv light a reagent! it would be a condition to carry out the reaction and if that what he wanted the other two answer would of both been nickle catalyst at 200 degree so had cl2 instead

xJEx

Deleted User wrote: »

If they are being ruthless with the marking scheme, I don't think it will. It all depends on the marking scheme though.

But why, what am I leaving out?
i said air contains oxygen so it would affect the ppm result in the end...

_LilyRose_

ahmdoda wrote: »

i was going to write uv light but i wondered how is uv light a reagent! it would be a condition to carry out the reaction and if that what he wanted the other two answer would of both been nickle catalyst at 200 degree so had cl2 instead

Yeah the 'reagent' threw me I was trying to think of chemicals! But is the nickel catalyst not for turning aldehydes, ketones into alcohols? And what's the 200 degree thingy?!

ahmdoda

_LilyRose_ wrote: »

Yeah the 'reagent' threw me I was trying to think of chemicals! But is the nickel catalyst not for turning aldehydes, ketones into alcohols? And what's the 200 degree thingy?!

yes im confused now my self dont bother with the 200 degree i just remember my teacher saying that the nickle has to be at 200 degrees but its never required

xJEx

xJEx wrote: »

But why, what am I leaving out?
i said air contains oxygen so it would affect the ppm result in the end...

They could specify that they want it mentioned that atmospheric O2 dissolves into the sample. Like I said, I would give you the marks but it will depend on the marking scheme.

ahmdoda

Deleted User wrote: »

They could specify that they want it mentioned that atmospheric O2 dissolves into the sample. Like I said, I would give you the marks but it will depend on the marking scheme.

im not sure if their going to be thats specific about it all that it says in my book is to prevent air bubbles containing oxygen from affecting the result but if they do i guess ur safe good thinking though

MarieCurie22

What were your dissolved oxygen in ppm??? I got 7.52

Also heat of neutralization....4.3kj?

And anyone do the oxidation q with the masses of Al and Fe??

xJEx

Deleted User wrote: »

They could specify that they want it mentioned that atmospheric O2 dissolves into the sample. Like I said, I would give you the marks but it will depend on the marking scheme.

Ok. for the reagent I said 'MnSo4 - manganese sulfate'' instead of manganese (II) sulfate - would i lose a mark or would it be okay cause i had the formula correct?
And what was the last bit, about it having to be done immediately?

mocker2012

xJEx wrote: »

Ok. for the reagent I said 'MnSo4 - manganese sulfate'' instead of manganese (II) sulfate - would i lose a mark or would it be okay cause i had the formula correct?
And what was the last bit, about it having to be done immediately?

Photosynthesis/Respiration by organisms in water change dissolved o2 levels in water over

MarieCurie22

xJEx wrote: »

Ok. for the reagent I said 'MnSo4 - manganese sulfate'' instead of manganese (II) sulfate - would i lose a mark or would it be okay cause i had the formula correct?
And what was the last bit, about it having to be done immediately?

I wrote the two as well id say it was a hard paper so theyd give you the marks....

xJEx

mocker2012 wrote: »

Photosynthesis/Respiration by organisms in water change dissolved o2 levels in water over

Hmm i didnt really know so I said the amount os dissolved oxygen can change when the sample is exposed to air and light?

ynwa14

The ordinary paper was HORRIBLE I thought gah. I dont care anymore. Never looking at this subject again.