All chemistry Doubts here :)

[xIshtar]

For Hydra:

The formula for the acid is C4H4O4 right.

So, it is an acid. As it is dibasic, 2 H+ ions for every one mole reacted.

Now, taking this into account, it should be possible to split it into two equal parts..

HOOCCH=HOOCCH

The truth is, the question is rather challenging, and I do not get the exact method behind the answer. I have drawn it out a couple of times and still nothing.

Maybe some body could enlighten us all. *Cough* haochen. *Cough*

but i dont know what question ur talking about ?? :Search:
can u tell me

and ill try to explain it

Q.P--> http://www.xtremepapers.me/CIE/Cambridg ... _qp_12.pdf
M.S--> http://www.xtremepapers.me/CIE/Cambridg ... _ms_12.pdf
Question 8
answer: "A" silver is a reactive metal ! how ? isn`t silver under copper in the reactivity series ??
why not "B" !!!!!!! OMG IT`S SOOOOOO TRICKY MAAAAN

A is the answer (the question is to choose the one which is not correct)
because electroplating isnt about the reactivity.
and it is not B because u need to have the metal salt to perform electroplating
so the metal can be transfer from the anode(metal) to the cathode(spoon)

hope i helped

Question:- http://www.xtremepapers.me/CIE/Cambridg ... _qp_33.pdf
5 (b) (iv)

Mark scheme:- http://www.xtremepapers.me/CIE/Cambridg ... _ms_33.pdf

I am not able to understand the meaning of the word "dibasic" and from where the double bond came

 

[HyDraZin3]

http://www.xtremepapers.me/CIE/Cambridg ... 7_qp_1.pdf
9th question
y the answer cant be barium sulphate? is it cuz it is insoluble in water?

 

[LimeReem]

http://www.xtremepapers.me/CIE/Cambridge%20IGCSE/0620%20-%20Chemistry/0620_w07_qp_1.pdf
9th question
y the answer cant be barium sulphate? is it cuz it is insoluble in water?

yup! barium sulphate is insoluble in water!

 

[brainiac]

yup hes right

 

[lavanyamane]

http://www.xtremepapers.me/CIE/Cambridg ... _qp_32.pdf
Q.6(d)(iii) ? Why is thallium sulfate precipitate green? How do we know that?

 

[xIshtar]

You know because it's a hydroxide and iron (ii), thus assume that the same rule applies as that with NaOH

 

[moonlight22]

Electrochemical simple cell:

reactions:

copper-->positive electrode
zinc-->negative electrode
electrolye: sulfuric acid
zinc----> zinc ion
copper---> hydrogen ions from acid reacts with it and gains electron and becomes a hydrogen gas

question: why copper electrode doesn`t loose electrons ?

Fuel cells:

Acidic electrolyte : I didn`t understand the reactions of oxygen and hydrogen why oxygen gains 4 electrons and not hydrogen ?
alkaline electrolyte : i didn`t UNDERSTAND

thanks XOXO

 

[moonlight22]

come on no 1 can answer this ?? :lol:

 

[lavanyamane]

I don't understand this stuff well enough to explain to to somebody, so sorry x

 

[MohammedNoor]

please can anyone help me to clear my doubts



* first...............................manufacture of steel*
*second..............................manufacture of ammonia
*third.................................what is oxidation and reduction.................plzzzzzzzzzzz

 

[LimeReem]

I already told u the manufacture of steel and ammonia on ur other topic =)
cause im in the mood of helping others ill clear ur other doubt!
Oxidation is loss of electrons (hydrogen) and gain of oxygen!
Reduction is gain of electron(hydrogen) and loss of oxygen!

 

[MohammedNoor]

I already told u the manufacture of steel and ammonia on ur other topic =)
cause im in the mood of helping others ill clear ur other doubt!
Oxidation is loss of electrons (hydrogen) and gain of oxygen!
Reduction is gain of electron(hydrogen) and loss of oxygen!

thnx but i post more in my topic plz see it and help me....................................thnx

 

[LimeReem]

Can someone help me with moles, I am seriously weak in that topic!!
http://www.xtremepapers.me/CIE/Cambridg ... _qp_31.pdf
last question 8(b)
I know Moles=Mass by Mr but im seriously getting confused

 

[JmCullen]

Can someone help me with moles, I am seriously weak in that topic!!
http://www.xtremepapers.me/CIE/Cambridg ... _qp_31.pdf
last question 8(b)
I know Moles=Mass by Mr but im seriously getting confused

40cm3 = 0.04dm3
0.04dm3 (times) 2mol/dm3 = 0.08mol (HCl used)

0.08 (divide) 2 = 0.04mol (CoCl2 formed) because ratio is 2:1 (2mol of HCl and 1mol of CoCl2) in the equation

0.04mol (CoCl2.6H2O) since same mol in equation(1:1), so their mol will be the same.

0.04 (times) 238 = 9.52g (mol times Mr)

0.08 mol (just copy the first answer)

6 (divide) 119 = 0.05 mol (mass divide Mr)

cobalt(II) carbonate is excess because only need 0.04mol. the ratio is 2:1. and it has 0.05mol. so, it is an excess..


hope you understand.
im not quite good in explaining calculation. hahaha

 

[LimeReem]

Can someone help me with moles, I am seriously weak in that topic!!
http://www.xtremepapers.me/CIE/Cambridg ... _qp_31.pdf
last question 8(b)
I know Moles=Mass by Mr but im seriously getting confused

40cm3 = 0.04dm3
0.04dm3 (times) 2mol/dm3 = 0.08mol (HCl used)

0.08 (divide) 2 = 0.04mol (CoCl2 formed) because ratio is 2:1 (2mol of HCl and 1mol of CoCl2) in the equation

0.04mol (CoCl2.6H2O) since same mol in equation(1:1), so their mol will be the same.

0.04 (times) 238 = 9.52g (mol times Mr)

0.08 mol (just copy the first answer)

6 (divide) 119 = 0.05 mol (mass divide Mr)

cobalt(II) carbonate is excess because only need 0.04mol. the ratio is 2:1. and it has 0.05mol. so, it is an excess..


hope you understand.
im not quite good in explaining calculation. hahaha

TYSSSMMM!! =DDDD :Yahoo!:

 

[JmCullen]

Can someone help me with moles, I am seriously weak in that topic!!
http://www.xtremepapers.me/CIE/Cambridg ... _qp_31.pdf
last question 8(b)
I know Moles=Mass by Mr but im seriously getting confused

40cm3 = 0.04dm3
0.04dm3 (times) 2mol/dm3 = 0.08mol (HCl used)

0.08 (divide) 2 = 0.04mol (CoCl2 formed) because ratio is 2:1 (2mol of HCl and 1mol of CoCl2) in the equation

0.04mol (CoCl2.6H2O) since same mol in equation(1:1), so their mol will be the same.

0.04 (times) 238 = 9.52g (mol times Mr)

0.08 mol (just copy the first answer)

6 (divide) 119 = 0.05 mol (mass divide Mr)

cobalt(II) carbonate is excess because only need 0.04mol. the ratio is 2:1. and it has 0.05mol. so, it is an excess..


hope you understand.
im not quite good in explaining calculation. hahaha

TYSSSMMM!! =DDDD :Yahoo!:

u're welcome!!!
glad that u understand