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AQA CHEM5 A2 Chemistry - 19th June 2013

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Reply 1920

What are you guys on about,

If there is covalent character in ionic substances, of course the enthalpy change is higher.

There is additional bonding so more energy is required.

Reply 1921

Arihant

anyone got january 2013 paper and mark scheme

Reply 1922

Bootala

Original post by AspiringGenius

yes

do they come up often?? :3

Reply 1923

marleyxd

Original post by frogs r everywhere

No. That would be an example of ligand substution. Ligand subsitution reactions can only occur with copper, chromium and cobalt.

No ligand substitution occurs in Al aswell.

Reply 1924

username1054067

Original post by AspiringGenius

Partial covalent character in an ionic lattic increases the lattice dissociation enthalpy. i.e. it takes more energy to break up the lattice.

Why then, does Al2O3's partial covalent character make it have a lower melting point than MgO?

Do you really want to know?

http://uk.answers.yahoo.com/question/index?qid=20110623025810AAhQHB6

It's beyond A level, just remember it's an exception

Reply 1925

mutld06

hey just wanted to ask what are back titrations...???

Reply 1926

MrMeep2580

Original post by Med_me

Thanks, and is the oxidising agent found there?

yerp!

Reply 1927

peebs123

Original post by Tasha_11

It's the same as the temperature at which the reaction IS feasible, because going above/ below this temperature will make the reaction feasible/ not feasible :smile:

Posted from TSR Mobile

ahh thank you :smile:

Reply 1928

AspiringGenius

Original post by Bootala

do they come up often?? :3

Well they come up in most exams- the big 5/6mark calculation is usually a back titration :redface:

Reply 1929

xDesertRose

Original post by frogs r everywhere

No. That would be an example of ligand substution. Ligand subsitution reactions can only occur with copper, chromium and cobalt.

Seriously???? Are u sure?

Reply 1930

havana-affair

When talking about bonding in ionic oxides, I know its ionic bonding but do you not talk about electrostatic attraction when saying why it has a high melting point?

Reply 1931

TeddyBasherz

Original post by yarshad

Do you really want to know?

http://uk.answers.yahoo.com/question/index?qid=20110623025810AAhQHB6

It's beyond A level, just remember it's an exception

Wow, I literally started to read the second paragraph and instantly lost my concentration lol.

Reply 1932

Jesss9

Original post by mutld06

hey just wanted to ask what are back titrations...???

I was about to ask this but I was scared it was stupidly obvious :tongue:

Reply 1933

livinglife24

Is question 7a on the Jan 13 paper just a drawing of 2 beakers, one with Fe2+ solution and other with hydrogen and salt bridge etc?

Reply 1934

tilownii

Please help me how do you draw the cell in question 7a jan 2013 and what colour is feh2o63+ thx

Reply 1935

flyylikejetz

what page is the Jan 13 paper & mark scheme on ?

Reply 1936

starfish232

Original post by marleyxd

No ligand substitution occurs in Al aswell.

Yes but Al isn't a transition metal so It shouldn't be a substitution reaction for Al...

Reply 1937

maansikalyan

What cell types is everyone revising? And how many advantages/hazards of each? I just got told to do rechargeable, fuel and zinc/carbon cells but I'm worried it's not enough:|