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All chemistry Doubts here :)

K

Keeemoman

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OK this is damn easy
It is double bond cause they mentioned at the beginning that it is unsaturated
And it is a weak acid so instead of H+,it is COOH+
so then it is shown clearly in the marking scheme as (COOH)2
and then continue formula you will get the same equation
Hope u got it!!!!!!!
 
H

HyDraZin3

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Keemoman, the answer is HOOCCH=CHCOOH but can we write it as CCOOHH=CHCHOO ? and how do u know if its a weak acid or not? and what is the meaning of 1 mole of acid produced 2 moles of H+ ? :unknown:
 
Z

zkapoor

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HyDraZin3 said:
Keemoman, the answer is HOOCCH=CHCOOH but can we write it as CCOOHH=CHCHOO ? and how do u know if its a weak acid or not? and what is the meaning of 1 mole of acid produced 2 moles of H+ ? :unknown:
Click to expand...

Firstly, H has a double bond with C ?
And secondly, you've only shown one (COOH) chain.
I would suggest, if you're getting confused with this type of question draw it out and count the bonds.
Btw 1 mole of acid makes 2 moles of H+ ions basically means that the anion of the acid has a double negative charge so there are 2 H+ ions per unit of acid.
Consider H2SO4. SO4 has a valency of 2- so 2 H+ ions are needed per unit to make the acid.
So, 1 mole of the acid will produce 2 moles of H+ ions.
Similarly, 1 mole of the acid you're talking about will have 2 of the (COOH) chain

Hope this helps
 
Z

zkapoor

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AStarHunter said:
guyz, the last problem in this paper (http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w06_qp_3.pdf) ---> Q8(c)(iii) ---> how do they know which one is saturated and which one is unsaturated.
Thnx in advance :D && sorry for my stupidity -.-"
Click to expand...

Doesn't matter. The answer is chromatography - as long as the products are different they will rise to different heights on a chromatogram. Boiling point will probably also work in this case (though it's not in the mark scheme)
 
A

AStarHunter

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zkapoor said:
AStarHunter said:
guyz, the last problem in this paper (http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w06_qp_3.pdf) ---> Q8(c)(iii) ---> how do they know which one is saturated and which one is unsaturated.
Thnx in advance :D && sorry for my stupidity -.-"
Click to expand...

Doesn't matter. The answer is chromatography - as long as the products are different they will rise to different heights on a chromatogram. Boiling point will probably also work in this case (though it's not in the mark scheme)
Click to expand...

thanx, but i meant (c)(iii), not (a)(iii) :D
 
K

Keeemoman

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For the first answer you have to follow the equation since if you try doing yours(I mean in the structural formula and not condensed)
and the second have you ever heard a strong acid called Maleic acid and thirdly what u said is 1 mole produces 2 moles of H+, this is dibasic
 
gary221

gary221

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gosh its getting too confusing!!!! :%) :%) :%) :%)

so does dibasic mean that the acid contains 2 H+ ions or sth??
 
Y

Yoyo1994

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Hello all, I've got a doubt that comes from October/November 2010. It is question 17, which states:

When pink crystals of cobalt(II) chloride are heated, steam is given off and the colour of the solid changes to blue.
CoCl2.6H2O (reversible reaction sign) CoCl2 + 6H2O
What happens when water is added to the blue solid?

Colour ---------- Temperature
A changes to pink ---------- decreases
B changes to pink ---------- increases
C remains blue ---------- decreases
D remains blue ---------- increases

I chose A but it seems the answer is B. I thought that it was A because when in the beginning heat was absorbed into the crystals it was endothermic and heat is increased in the crystals and decreased in the surroundings. When water is added the whole thing is reversed and it is exothermic where heat is lost to the surroundings by the crystals and the temperature in the crystals decreases and increases in the surroundings.
Now, if I thought they were referring to the surroundings I would have chosen B but they clearly asked about what happens in the crystals when they used "colour" and "temperature".
Can someone explain to me why I got this wrong? Thanks.
 
Z

zkapoor

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Right, so the answer is that temperature increases. This is rather simple. When they speak of temperature UNLESS THEY SAY OTHERWISE (or in a diagram position the thermometer in the product) they mean temperature of the surroundings.
Think of it like this, how can you measure the temperature change of the paper? You'd have to put the thermometer inside it, which is impossible. The closest you can get is right next to the paper which is part of the *drumroll please* surroundings =P
 
Z

zkapoor

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AStarHunter said:
zkapoor said:
AStarHunter said:
guyz, the last problem in this paper (http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w06_qp_3.pdf) ---> Q8(c)(iii) ---> how do they know which one is saturated and which one is unsaturated.
Thnx in advance :D && sorry for my stupidity -.-"
Click to expand...

Doesn't matter. The answer is chromatography - as long as the products are different they will rise to different heights on a chromatogram. Boiling point will probably also work in this case (though it's not in the mark scheme)
Click to expand...

thanx, but i meant (c)(iii), not (a)(iii) :D
Click to expand...

My mistake, apologies. Keemoman is right
Dibasic acids have 2 H+ ions and can hence form 2 varieties of salts - acidic (NaHSO4) or neutral (Na2SO4)
 
xIshtar

xIshtar

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Dibasic refers to the fact that for every mole of acid used, there are 2 moles of H+ ions.
 
xIshtar

xIshtar

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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*
 
Z

zkapoor

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xIshtar said:
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*
Click to expand...

Dude, you've got a double bond between your H's. I'm telling you, if you draw it out you'll get it. the answer is HOOC-CH2=CH2-COOH
Think about it. 1 Carbon atom per half is being used for the carboxylic acid bond leaving exactly 1 carbon atom per half (or 1 pair in total) to make a double bond. Naturally this pair must be in the middle. Hence HOOC-CH2=CH2-COOH
 
xIshtar

xIshtar

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zkapoor said:
xIshtar said:
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*
Click to expand...

Dude, you've got a double bond between your H's. I'm telling you, if you draw it out you'll get it. the answer is HOOC-CH2=CH2-COOH
Think about it. 1 Carbon atom per half is being used for the carboxylic acid bond leaving exactly 1 carbon atom per half (or 1 pair in total) to make a double bond. Naturally this pair must be in the middle. Hence HOOC-CH2=CH2-COOH
Click to expand...


Apologies, I meant to write HOOCCH=HCCOOH..

I get your answer, but there are only supposed to be 4 Hydrogens? Yours has 6.. This is where I got confused :p
 
Z

zkapoor

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xIshtar said:
zkapoor said:
xIshtar said:
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*
Click to expand...

Dude, you've got a double bond between your H's. I'm telling you, if you draw it out you'll get it. the answer is HOOC-CH2=CH2-COOH
Think about it. 1 Carbon atom per half is being used for the carboxylic acid bond leaving exactly 1 carbon atom per half (or 1 pair in total) to make a double bond. Naturally this pair must be in the middle. Hence HOOC-CH2=CH2-COOH
Click to expand...


Apologies, I meant to write HOOCCH=HCCOOH..

I get your answer, but there are only supposed to be 4 Hydrogens? Yours has 6.. This is where I got confused :p
Click to expand...

Oh, whoops, sorry. I meant to write HOOCHC=CHCOOH
 
haochen

haochen

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xIshtar said:
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*
Click to expand...

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

and ill try to explain it :)

moonlight22 said:
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
Click to expand...

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 :D
 
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