Thx, and I'm doing Edexcel. Can someone help me answer this question:

Sodium iodide reacts with concentrated sulp[huric acid to give iodine, not hydrogen iodide. Explain why iodides react differently from chlorides in this case. (2 marks)

I wrote:

the chloride is a weaker reducing agent than the iodide, so the sulphur remains in a higher oxidation state in the reaction with chlorine and cannot accept the hydrogen ion...?

I don't understand the question though to be honest, that was me just blagging it.

Reply 7

Dust

urm i dunno is it to do with how chlorine has less shielding therefore is more reactive so it will form HCl whereas Iodine is less reactive due to more sheilding and therefore doesnt react with the hydrogen very easily to form HI??

thats just a guess...

Reply 8

john !!

OP

14

Dust

urm i dunno is it to do with how chlorine has less shielding therefore is more reactive so it will form HCl whereas Iodine is less reactive due to more sheilding and therefore doesnt react with the hydrogen very easily to form HI??

thats just a guess...

When the iodine reacts, is gains an electron, obviously chlorine will gain that electron more readily because the shell is closer to the nucleus, so yes maybe you could say the iodide does not provide a strong enough nuclear pull to bond with the hydrogen.

Reply 9

Dust

lol sum1 gimme that paper... i;m going mad if i dont get a blimmin A on the paper.. then i can 4get my only uni offer argh!

Reply 10

jag_jatt

Dust

lol sum1 gimme that paper... i;m going mad if i dont get a blimmin A on the paper.. then i can 4get my only uni offer argh!

haha i doubt it was the actual paper - but hearing that the paper had been leaked makes me well mad cuz its unfair - but den again - lifes a bitch!

Reply 11

cipapfatso

mik1a

Thx, and I'm doing Edexcel. Can someone help me answer this question:

Sodium iodide reacts with concentrated sulp[huric acid to give iodine, not hydrogen iodide. Explain why iodides react differently from chlorides in this case. (2 marks)

I wrote:

the chloride is a weaker reducing agent than the iodide, so the sulphur remains in a higher oxidation state in the reaction with chlorine and cannot accept the hydrogen ion...?

I don't understand the question though to be honest, that was me just blagging it.

As sulphuric acid is an acid, and therefore a proton donor, it should give up hydrogen ions to the halide ions to form the hydrogen halide gases. This is in fact what occurs, but as concentrated sulphuric acid is also a powerful oxidizing agent further reaction is possible. Hydrogen chloride is not easily oxidized, so the reaction between concentrated sulphuric acid and potassium chloride produces only this gas. With the iodide ions, they are oxidised to HI and then further into I2. this is the same with Bromine (though not to the same extent).
You're on the right lines. It's because iodide ions are greater reducing agents - remember the stronger the reducing agent the easier it is oxidised. It sounds obvious but its easily misinterpreted.

Reply 12

Dust

dang yr good

Reply 13

greenie787

what does it mean when something is catalytically hydrogenated?

Reply 14

Hawk

1

Hi,

Can someone give me the correct definition of Hydration Enthalpy, in my notes the last bit has been cut off, so far I have,

The enthalpy change when one mole of gaseous ions dissolves in sufficient water to produce...

Thanks

Reply 15

cipapfatso

greenie787

what does it mean when something is catalytically hydrogenated?

Hydrogenation (reduction) of a compound using a catalyst. For example benzene is hydrogenated to cyclohexane with a nickel catalyst, hydrogen (and a temp 200 C and pressure of 30atm). For the compound to be reduced a catalyst is used - frequently nickel. It is also used to saturate compounds like unsaturated fats to make them saturated to make things like margarine.

C6H6 + 3H2 ---Ni catalyst---> C6H12

Reply 16

Dust

Hawk

Hi,

Can someone give me the correct definition of Hydration Enthalpy, in my notes the last bit has been cut off, so far I have,

The enthalpy change when one mole of gaseous ions dissolves in sufficient water to produce...

Thanks

enthaply change when one mole of gaseous ions are dissolved in excess water to produce one mol of aqueous ions under standard conditions in their standard statesa (1atm 298 k)

wow i still remember *looks shocked*

Reply 17

hero

1

does anyone here feel confident with this chemistry exam?
The board Im on is AQA and I have modules 1 to 3 tomorrow...nervous
I still dont remember everything :frown:

Reply 18

Dust

i;/m seriously begginning to panic..

Chemistry (last minute revision) !!!

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