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OCR Chemistry F322~ 4th June 2013~ AS Chemistry

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Reply 1120

Dr. Django

Original post by needtosucceed=)

yea the cl can go on any of the carbons :smile:

for 4a. part 1, its told you the enthalpy change is -92 but thats when 2 moles of nh3 form, so for one mole its just half it.
part 2, well catalysts lower activation energy so anything less than 250 is fine (except -ve numbers)
for part 3, whenever your finding out the activation energy of a reversed reaction you just add the enthalpy change and activation energy of the forward reaction together. ignore the negative sign on the enthalpy change. so 92 + 250 = 342

Thanks

Reply 1121

Felttip

Catalytic converter is a mind fock!!!

Reply 1122

JimmyA*

Original post by Sara_A

Q5ei in the June 11, i dont get how the shape around the first carbon atom is tetrahedral

Carbon forms covalent bonds. It is covalently bonded to 1 other carbon and 3 hydrogen atoms. This means there are 4 bonding pairs. From F321 you know this is tetrahedral.

Reply 1123

needtosucceed=)

Original post by Sara_A

Q5ei in the June 11, i dont get how the shape around the first carbon atom is tetrahedral

any carbons that arent double bonded to other carbons have a tetrahedral shape. the carbons making the bond with hydrogen so its tetrahedral

Reply 1124

Jimmy20002012

Original post by Sara_A

Q5ei in the June 11, i dont get how the shape around the first carbon atom is tetrahedral

Not seem the question, but if you have a C-C bond the shape will always be tetrahedral and have a bond angle of 109.5 degrees. However if you have a double C-C bond the shape will be triglanor planer with a bond angle of 120 degrees :smile:

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Reply 1125

niceguy95

Original post by Ché.

As long as you get the grade, you're super good!
Well done for the 82/90 - I am looking to get around 82-84 myself!
Are you in Year 13!?

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Year 12

Reply 1126

JimmyA*

Original post by Felttip

Catalytic converter is a mind fock!!!

Look at the mark scheme for Q4b) on the Jan 2011 paper. Thats all you need to know.

Reply 1127

scorpio22

Original post by niceguy95

Do the people here understand the chemistry or just know how to answer the questions

thats an actually really good question.And one i find asking myself.
There is some areas such as mechanisms: electrophillic addition and nucleophillic sub.. learn the dipoles,movement of electrons etc
just learn it because it will come up somehow

boltzmann:temp or catalyst guranteed to come up
catalyst convertor process almost always comes up.

carbon capture almost comes up.
polymers;alcohol

I think this exam is about attention to detail, there is so many areas to make mistakes like writing incomplete instead of complete combustion.
drawing full displayed instead of sketal, significant figures. when it requests
There are also so many areas to get marks:

one thing that will definitely come up is definitions and enthalpy calculations.thats one i would encourgae to understand.
how to calculate formation from combustion
combustion from formation
enthalpy reaction
the reverse reaction activation etc

Reply 1128

Hello...

Original post by JimmyA*

Yep and that is because a Carbon-Carbon double bond causes a kink in the chain shortening the length of the chain.

I dont think the length of the chain is affected by the Carbon-Carbon double bond, You'd still have the same number of carbon atoms in the chain, the length would only be affected if it was branched...
After Hydrogenation there are more C-H bonds so more dipoles can form so more VDW forces can form.

Reply 1129

niceguy95

Original post by Felttip

Catalytic converter is a mind fock!!!

Not really bro

All you need to know is

Basically it's the conversion of harmful gases into less harmful ones (found in engines)

So for instance carbon monoxide and nitrogen monoxide into carbon dioxide and nitrogen

So if the question came up, just write

CO & NO adsorb onto surface od catalyst
Lowers the activation energy and bonds weaken
CO2 & N2 desorb from surface

And that's three marks

If the ask for which metal just say palladium

Reply 1130

Felttip

can anyone explain catalytic converter and carbon capture for me please

Reply 1131

scorpio22

Original post by needtosucceed=)

me too! let's hope its a nice paper..
hows f325 revision going? I've definitely done more for f322 even though f325s harder :/

its non exsistent. I did most of it last half term because i knew i would be swamped with other revision around now.

i have 2 exams next week on tuesday. i wanna get them out of the way and just fully go 100% mode on f325.. i just need time on transitions; enthalpy and a few calculations.
I want a C, last time my result was really bad lool. I know i am not going to get an A in f325 therefore i will get an A in f322 and f324 which are easier

Reply 1132

Sara_A

Original post by Jimmy20002012

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Compound G is CH3CH=CHCH3
So it does have a double boind, but according to the markscheme the shape around carbon atom number 1 is tetrahedral but the shape around carbon atom number 2 is trigonal planar

Reply 1133

needtosucceed=)

Original post by scorpio22

did u do f325 in january? we did it as a mock in class and it was killer! same ive got 2 on tuesday :/ are u aiming for an A overall?

Reply 1134

needtosucceed=)

Original post by Sara_A

its not just if the compound has a double bond or not, its referring to the specific carbon. So the carbon which is tetrahedral is the single bonded one and the one thats double bonded is the trigonal planar one.

Reply 1135

niceguy95

Original post by Felttip

can anyone explain catalytic converter and carbon capture for me please

Carbon capture storage consists of 2 stages

Co2 is injected deep into the ocean

It react with metal oxides to form stable carbonates

Regarding This topic, it is what scientists do to reduce global warming

Other methods include providing scientifical evidence global warming is occurring to the government

Also following the Kyoto protocol

Reply 1136

JimmyA*

Original post by Hello...

It is it forms a kink (like a zig zag shape), you do it in F324, so there will be less points of contact, hence why unsaturated triglycerides are liquid at room temperature(oils) and saturated triglycerides are solid at room temperature (animal fats, butter etc.).