Chemistry Help HERE ONLY !!

[MaNa]

thanx     u sent me 3 times!!!!!!!!!!!!!!!!coooooooooooool

they are three different thing
mark scheme
etc:D
oi dont forget +rep:)

[MaNa]

 i have one confusion
in electrolysis
the cation the most reactive stays in the solution or goes to the anode?
similary for the anions

[crypsAnity]

the most reactive stays in the solutions .. for both of them .. =]

p.s just revised it an hour back.. hehe

[emi]

thanks bani ,, you;r great !

[emi]

2)
(c) Each tablet contains the same number of moles of CaCO3 and MgCO3. One tablet
reacted with excess hydrochloric acid to produce 0.24 dm3 of carbon dioxide at r.t.p.
CaCO3 + 2HCl ----> CaCl2 + CO2 + H2O
MgCO3 + 2HCl ----> MgCl2 + CO2 + H2O
(i) Calculate how many moles of CaCO3 there are in one tablet.
number of moles CO2 = ..............    ( i got this one  0.24/24 = 0.01 )
number of moles of CaCO3 and MgCO3 = ..............  ( how do i get this  one ? is it just by common sense or is there formula ?)
number of moles of CaCO3 = ..............  ( and wat formula we used to get this one ? )

(ii) Calculate the volume of hydrochloric acid, 1.0 mol /dm3, needed to react with one
tablet.
number of moles of CaCO3 and MgCO3 in one tablet = .............. ( i got this one because its says from c i )
Use your answer to (c)(i).
number of moles of HCl needed to react with one tablet = .............. ( how do i get this one ?  why is is 0.02)
volume of hydrochloric acid, 1.0 mol /dm3, needed to
react with one tablet ..............



some one help me please ?

[ramezamgad]

emi
0.01 moles of CO2 were produced from the total reaction
the tablet has the same no. of moles of CaCO3 and MgCO3
so the no. of moles of CaCO3 and MgCO3 is 0.01 moles also
the no. of moles of CaCO3 only is 0.01/2 = 0.005

moles of HCl=0.01x4
no.=V x C
0.04=V x 1
V=0.04 dm3=40cm3

[emi]

can some one give me mark scheme for November 2003 paper3 ?  the one on Free exam paper is totally unrelated

[astarmathsandchemistry]

can some one give me mark scheme for November 2003 paper3 ?  the one on Free exam paper is totally unrelated

there u go

[aquarian93]

u guys,
for exothermic: we say the temp increases
and endothermic: the temp decreases

rite?

so this is abt the surrounding and not the reagent?

pls help!

[thukon]

A classmate told me a good mnemonic for the reactivity series, but it goes by the first letter of the element
Please- Potassium
Send- Sodium
Lord- Lithium
Charles- Calcium
McClain- Magnesium
A- Aluminium
Zebra- Zinc
If- Iron
The- Tin
Lame- Lead
Horse- Hydrogen
Cannot- Copper
Munch- Mercury
Sweet- Silver
Grass- Gold
No point in adding one for platinum, because it goes at the end anyway. Where does carbon go in this?

@aquarian. In exothermic, more heat is given out than taken in by the reaction. In endothermic, more heat is taken in than given out.

[THEIGBOY]

Guyz how do I make the structural Formula.....(i know the formulas themselves but not the structural formulas....
Tell me which one... and do tell me if ur sure or not....
I think we have to use number 2 but i'm not sure...

On the picture I drew....
1. Structural formula (lewis structure)
2. Also structural formula (different type) (text structure)
3. Skeletal formula
4. Chemical formula
1 & 2 both are structural formulas...
But in the exam when they ask for structural formula do i draw number 1 or number 2???
i.e. text structural formula or lewis structural formula?
Thanks in advance
THEIGBOY
By the way if there is need for any ppapers or marking schemes do tell me... i have most, if not all of them from 1999 onwards....AND
GOOD  BESTEST OF LUCK!!!!!!!!!!!![/shadow][/glow][/color][/font]
(i know there is no such word as "bestest" but still...)

[aquarian93]

u guys,
for exothermic: we say the temp increases
and endothermic: the temp decreases

rite?

so this is abt the surrounding and not the reagent?

pls help!

u guys pls help!

[thukon]

@aquarian. I posted ur answer.

@igboy. I would draw the first 1. I dont think it matters, but the 1st one is more informative, so i prefer it. The second one is called condensed structural formula or something like that.

[THEIGBOY]

u guys,
for exothermic: we say the temp increases
and endothermic: the temp decreases

rite?

so this is abt the surrounding and not the reagent?

pls help!

When the reaction is endothermic.... The surroundings will cool down...e.g. the beaker may cool down....
When the reaction is exothermic..... the surrounding will heat up..... e.g. the beaker may heat up....
and yes...they are talking abt the surroundings....

@thukon ---->
Carbon comes after aluminium and before zinc...hope it helps

[THEIGBOY]

Guyz how do I make the structural Formula.....(i know the formulas themselves but not the structural formulas....
Tell me which one... and do tell me if ur sure or not....
I think we have to use number 2 but i'm not sure...

On the picture I drew....
1. Structural formula (lewis structure)
2. Also structural formula (different type) (text structure)
3. Skeletal formula
4. Chemical formula
1 & 2 both are structural formulas...
But in the exam when they ask for structural formula do i draw number 1 or number 2???
i.e. text structural formula or lewis structural formula?
Thanks in advance
THEIGBOY
By the way if there is need for any ppapers or marking schemes do tell me... i have most, if not all of them from 1999 onwards....AND
GOOD  BESTEST OF LUCK!!!!!!!!!!!![/shadow][/glow][/color][/font]
(i know there is no such word as "bestest" but still...)

thanks.
I was just confused in 1 & 2, i made the rest in case it helps sum1....
Number 2 is called text structural formula, number 1 is called Lewis Structural formula....just so every1 knows