Chemistry: Post your doubts here!

[syed1995]

Are you sure? I thought that
Mg + 2 H2O(l) --> Mg(OH)2 + H2 (slow)
Mg + H2O(g) --> MgO + H2 (fast)

That's correct. But Mg only very slightly hydrolyzes.. so if one writes no reaction or very slow reaction he should get the mark.

 

[knowitall10]

from which book have u snapped this

From the older version of the orange one.. right now, we have the orange one right?
yeah, the book that was endorsed by Cambridge two years ago. umm.. wait, i'll post a pic.

 

[knowitall10]

CAN YOU TELL ME REACTIONS OF GROUP II AND PERIOD III WITH HCL AND H2O AND THEIR PH AND OBSERVATION IT IS CONFUSING

Don't you use your Chemistry text book? It's pretty clear there; to get rid of the confusion, write the formulas down and make tables the way you would remember. I know, i really hate periodicity and the group 2 and 7 chapter! Whatever happened to the phrase: "The brain is like a sponge".
:/

 

[A star]

That's correct. But Mg only very slightly hydrolyzes.. so if one writes no reaction or very slow reaction he should get the mark.

u know a METAL or a NON metal dont hydrolize in water their COMPOUNDS hydrolize so dont mix the two up

 

[knowitall10]

CAN YOU TELL ME REACTIONS OF GROUP II AND PERIOD III WITH HCL AND H2O AND THEIR PH AND OBSERVATION IT IS CONFUSING

or download this revision guide; its an excellent summary of everything.
http://www.hoddereducation.co.uk/Ti..._A_Level_Chemistry_Revision_Guide_for_CIE.htm

 

[knowitall10]

May june 11 53
1d(iiii)

the mark scheme says temp of both reagents taken or temp taken immediately after mixing.
What exactly is your question?

 

[ZainH]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_21.pdf

Q2)d)

Isn't reaction 1 the one where Ca goes to CaCl2? How would a solouble sulfate be an appropriate reagent? Explanation please

 

[syed1995]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_21.pdf

Q2)d)

Isn't reaction 1 the one where Ca goes to CaCl2? How would a solouble sulfate be an appropriate reagent? Explanation please

HAHA ANOTHER ONE! .. atleast i am not alone over here.. I also didn't read the reaction 1 word written in the table when i first read it.. I practically read the table 3-4 times but still didn't find where reaction 1 was.. But a guy on XPF helped me...

http://puu.sh/2NhNW.png

Check the W--> Z reaction.. that's labelled as reaction 1 .. Nitrate to Sulfate...

 

[knowitall10]

Oh my God. I give in! Can someone please tell me where on earth to we place the thermometer when we're drawing the apparatus in Paper 5, M/J 11 v3 Q1 (c)? (I take my reply to Tkp back- i think i get what he's asking...)

 

[ZainH]

HAHA ANOTHER ONE! .. atleast i am not alone over here.. I also didn't read the reaction 1 word written in the table when i first read it.. I practically read the table 3-4 times but still didn't find where reaction 1 was.. But a guy on XPF helped me...

http://puu.sh/2NhNW.png

Check the W--> Z reaction.. that's labelled as reaction 1 .. Nitrate to Sulfate...

Oh wow.. How the he- ?
...
Laaaaaaame, alteast I'm not alone xD . Thanks btw.

 

[knowitall10]

Oh my God. I give in! Can someone please tell me where on earth to we place the thermometer when we're drawing the apparatus in Paper 5, M/J 11 v3 Q1 (c)? (I take my reply to Tkp back- i think i get what he's asking...)

and even if i finally manage to draw the apparatus based on my AS practicals, how do we heat the solution? Can someone please draw a neat diagram?

 

[Soldier313]

ok see...

O2/OH^- = 0.4V and F/F^- = 2.87 so OH ion is easier to be oxidized than F^- so O2 will form at the anode..got it ? BUT i don't know why the mark scheme gives a wrong answer to this method with Br not SO4 but for the cations it gives all the answers right..do u solve it that way too?

exactly, that's my confusion, using the same method with Br gives a diff answer :/

 

[iKhaled]

exactly, that's my confusion, using the same method with Br gives a diff answer :/

using the other method that i showed u gives all of them correct values but i wonder why they dont give the same values with the potential electrodes if anyone here knows why or u know why then please do tell me because i want to know the reason now too..

 

[falcon678]

guys question 14...can u please explain how??

 

[ZainH]

What are the reagents/conditions for an elimination reaction and why?

 

[falcon678]

What are the reagents/conditions for an elimination reaction and why?

H2SO4 and alcoholic NaOH for elimination.......i dun knw y thou...

 

[knowitall10]

guys question 14...can u please explain how??

Write down the reaction of each of the four choices and use the mole ratio to figure out the masses. then see the mass of the gas produced and you'll get the answer. it's a long working but pretty simple.

 

[falcon678]

Write down the reaction of each of the four choices and use the mole ratio to figure out the masses. then see the mass of the gas produced and you'll get the answer. it's a long working but pretty simple.

thanks!

 

[ZainH]

H2SO4 and alcoholic NaOH for elimination.......i dun knw y thou...

Hm, what about the condition?

 

[Tkp]

the mark scheme says temp of both reagents taken or temp taken immediately after mixing.
What exactly is your question?

actually i didnt get for the 1 d iv
cn u please explain it?didnt get the part thats written in the ms