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Author Topic: CHEM AND BIO HELP AND TIPS HERE  (Read 357226 times)

Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2235 on: May 25, 2010, 08:07:43 am »
Morning guyz, wen do ur exams start??
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2236 on: May 25, 2010, 08:09:24 am »
Quote from: Kimo Jesus on May 25, 2010, 05:03:40 am
alright can u check the firsst post on this page??

and this  1 tooo

whyy?

not B ..lead is also a trans metal

but PbBr2 is SUPPOSED to be white
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2237 on: May 25, 2010, 08:10:15 am »
Quote from: A@di on May 25, 2010, 08:07:43 am
Morning guyz, wen do ur exams start??

Chem p1 and French p2 .. DONE ;)
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2238 on: May 25, 2010, 08:10:57 am »
Quote from: Kimo Jesus on May 25, 2010, 05:03:40 am
alright can u check the firsst post on this page??

and this  1 tooo

whyy?

not B ..lead is also a trans metal

wats the answer? A??
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2239 on: May 25, 2010, 08:11:30 am »
Quote from: ~VIN1094~ on May 25, 2010, 08:10:15 am
Chem p1 and French p2 .. DONE ;)

exam done?? so y are u guyz discussing it?
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2240 on: May 25, 2010, 08:15:45 am »
Quote from: Kimo Jesus on May 25, 2010, 05:30:17 am
asnwer is D???

is it caz CO + O2  is exothermic?

yes it is used as a fuel in the industries .. nitrogen on its own is not combustible 
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2241 on: May 25, 2010, 08:16:05 am »
Quote from: A@di on May 25, 2010, 08:11:30 am
exam done?? so y are u guyz discussing it?

umm .. only for me :P
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2242 on: May 25, 2010, 08:17:17 am »
Quote from: Lariemeeva on May 25, 2010, 07:17:41 am
Exactly, I actually studied it pretty well and then I read all those posts about concentrated and stuff and they've been pretty confusing since I know that Aq means it is dissolved in water.  

Anyways Oct/Nov 2008 Q3, Why is it Aqueous lead (II) nitrate and not dilute sulfuric acid?

And also M/J 2009 Q26.
What does the fact that it's green has to do with anything?

3)Lead Nitrate + Ba2+ + I- = Lead iodide + Barium nitrate. (soluble, thus will dissociate back into ions)

Lead iodide insoluble, yellow ppt. Barium nitrate, soluble.

with H2SO4, barium sulfate, insoluble, wont dissociate to ions, thus no Ba2+ ions...
Green - Iron salt

thus iron - high melting poinbt high density
« Last Edit: May 25, 2010, 08:21:09 am by A@di »
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Offline Xainalley

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2243 on: May 25, 2010, 08:17:45 am »
how did chem p1 go ppl?? bio p31 WUZ hard n LOOONG.....WAAYY too mch wrtin n ecology....
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Offline Lariemeeva

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2244 on: May 25, 2010, 08:18:45 am »
Oct/Nov 2008 Q3, Why is it Aqueous lead (II) nitrate and not dilute sulfuric acid?

And also M/J 2009 Q26.
What does the fact that it's green has to do with anything?

Oct/Nov 2008 Q15, Why is it A (Decrease of 20) I did the calculations and I got 5?

Can anyone please help on those questions??

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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2245 on: May 25, 2010, 08:20:15 am »
Quote from: Xainalley on May 25, 2010, 08:17:45 am
how did chem p1 go ppl?? bio p31 WUZ hard n LOOONG.....WAAYY too mch wrtin n ecology....

We are not allowed to say anything about the paper ;)
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2246 on: May 25, 2010, 08:22:05 am »
Quote from: Lariemeeva on May 25, 2010, 08:18:45 am
Oct/Nov 2008 Q3, Why is it Aqueous lead (II) nitrate and not dilute sulfuric acid?

And also M/J 2009 Q26.
What does the fact that it's green has to do with anything?

Oct/Nov 2008 Q15, Why is it A (Decrease of 20) I did the calculations and I got 5?

Can anyone please help on those questions??



3)Lead Nitrate + Ba2+ + I- = Lead iodide + Barium nitrate. (soluble, thus will dissociate back into ions)

Lead iodide insoluble, yellow ppt. Barium nitrate, soluble.

with H2SO4, barium sulfate, insoluble, wont dissociate to ions, thus no Ba2+ ions...

26)Green - Iron salt

thus iron - high melting poinbt high density

15) Endothermic, so heat taken in. Decrease of 20 degrees. 5grams in 500cm^3 will take in more heat. U might have used direct proportion in ur calculations, its inversely proportional here...
« Last Edit: May 25, 2010, 08:39:42 am by A@di »
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2247 on: May 25, 2010, 08:23:38 am »
Quote from: Lariemeeva on May 25, 2010, 08:18:45 am
Oct/Nov 2008 Q3, Why is it Aqueous lead (II) nitrate and not dilute sulfuric acid?

And also M/J 2009 Q26.
What does the fact that it's green has to do with anything?

Oct/Nov 2008 Q15, Why is it A (Decrease of 20) I did the calculations and I got 5?

Can anyone please help on those questions??



Oct/Nov 2008 Q3
aqueous lead(II) nitrate combines with barium iodide to form lead iodide which is insoluble and yellow in colour .. leaving behind Ba2+ ions

 M/J 2009 Q26.
A - because the "transition metals" form coloured salt compounds

which hav a high meting pt and high density
« Last Edit: May 25, 2010, 08:27:58 am by ~VIN1094~ »
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Offline Xainalley

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2248 on: May 25, 2010, 08:27:39 am »
Quote from: ~VIN1094~ on May 25, 2010, 08:20:15 am
We are not allowed to say anything about the paper ;)
i didnt ask nythn ....i meant hard or eazi..... :)
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Offline Lariemeeva

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #2249 on: May 25, 2010, 08:32:57 am »
A@di, sorry, I still don't understand Oct/Nov 2008 Q15 but thanks for the other explanations.
By the way, can list down all the important metals/transition metals/non-metals with their colours and their salts' colours?
And if Barium nitrate (or any other soluble substance) is soluble, it means we can  break it down into it's ions? Therefore, we can say that Barium is formed? And the insoluble substance is what gives off the precipitate?
« Last Edit: May 25, 2010, 08:37:23 am by Lariemeeva »
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