Year 12s: what will be the first way you research your future options? >>

OCR AS - Chemistry Unit F322 - Chains, energy and resource - REVISION!

Scroll to see replies

Electrophillic addition - HBr/HCl/HI
-electrophile attracted to the electron rich region/centre/atom where it accepts a pair of electron to form a covalent bond.

for reaction
C4H9OH + HCl = C4H9Cl + H2O why is it nucleophillic substitution?

Reply 441

lebrondd

Original post by hash007

for reaction
C4H9OH + HCl = C4H9Cl + H2O why is it nucleophillic substitution?

The Cl of HCL is slightly electronegative so acts as a nucleophile

ignore all that I dont know what Im talking about :frown:

(edited 12 years ago)

Reply 442

arvin_infinity

There are not enough questions on greeen chemistry..!!
Need 20 more marks in this crappy exam

Reply 443

786girl

1. if u hve nucleophilic substituition and use NH3 would you draw NH2- with a lone pair?

2.can someobe give me an easy full scoring definition of BOND ENTHALPY and AVG. BOND ENTHALPY.

3.xplain the importance of controlling global warming caused by atmospheric increase in greenhouse gases (???)

4. outline role played by chemists ???

5. PRINCIPLES?!?!?!

boooorrriiiinggggggggggggg

lol

Reply 444

786girl

i love this exam <3

minus the green chemistry *pukes*

Reply 445

timkench

Original post by hash007

for reaction
C4H9OH + HCl = C4H9Cl + H2O why is it nucleophillic substitution?

i swear thats electrophillic addition?

Reply 446

touran22

there is soo much technicality in this exam...small minor errors will cost you marks. i thought i was confident but now im just plain scared. :frown:

Reply 447

timkench

as far as i'm aware electrophillic addition - arrow will go from double c=c bond to the other reactant whereas nucelophilic substitition is where theres a negative ion which attack the back of a halogenoalkane?

i reckon following the trends of past papers, there'll be loads on the environmental effects of like CFCs PVC etc

Reply 448

Bright

Original post by timkench

i swear thats electrophillic addition?

That's what I thought :s-smilie:

Reply 449

Bright

Quick question guys.

In the revision notes, why did the person do q = - mx c x delta t is it not m x c x delta t?

:s

Reply 450

timkench

Original post by Bright

Quick question guys.

In the revision notes, why did the person do q = - mx c x delta t is it not m x c x delta t?

:s

you always change it minus at the end of the question anyway so maybe thats why?

Reply 451

yesioo

There are not enough questions on greeen chemistry..!!
Need 20 more marks in this crappy exam

You and me both!

Hmm questions.

Why do bond enthalpies have positive values?

"The rate of a chemical reaction increases as temperature is increased because there are more collisions".

Discuss tot what extent this statement is true and describe any other factors that should be considered when looking at the effect of temperature on rate of reaction.

Explain why C02 contributes more to global warming than CH4 even though it has a lower greenhouse factor?

Reply 452

hash007

Original post by timkench

i swear thats electrophillic addition?

I thought it was electrophillic substitution as the OH was being substituted for a Cl, but mark scheme says Nucleophillic substitution.

Reply 453

hash007

Can someone quickly run through Greenhouse gas effect :colondollar:

How to answer it if it was a 6 marker!

Reply 454

touran22

Original post by Bright

Quick question guys.

In the revision notes, why did the person do q = - mx c x delta t is it not m x c x delta t?

:s

its M x C x DeltaT

i swear thats electrophillic addition?

nah its nucleophilic sub becuase H-CL is non polar and CL has a lone pair of e- it can donate!

Reply 455

Bright

Original post by timkench

you always change it minus at the end of the question anyway so maybe thats why?

Why do you always change it to minus at the end of the question? :colondollar:

(is it always exothermic?)

Reply 456

786girl

Outline early developments in mass spec... -_-

Reply 457

timkench

Original post by touran22

its M x C x DeltaT

nah its nucleophilic sub becuase H-CL is non polar and CL has a lone pair of e- it can donate!

pretty sure H-Cl has dipols due to large difference in electronegativities, and hetrolytic fission takes place, check the textbook

Reply 458

hash007

Also what are the conditions for all the reactions? Does anyone have like a summary sheet of them all, would be very helpful? :smile:

Reply 459

timkench

Original post by Bright

Why do you always change it to minus at the end of the question? :colondollar:

(is it always exothermic?)

rise in temp of surroundings = fall in temp of the system

if there is a fall in temperature the sign will come out as a minus which would be changed to a positive if you do start temp. minus finish temp. so yeah always swap the sign because you are measuring the surroundingss