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Author Topic: Chemistry Help HERE ONLY !!  (Read 106120 times)

Offline ZeroZero82

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Re: Chemistry Help HERE ONLY !!
« Reply #240 on: May 29, 2009, 11:04:16 am »
Ok here's a question, list the uses of ployesters.
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #241 on: May 29, 2009, 11:07:47 am »
Quote from: ZeroZero82 on May 29, 2009, 11:04:16 am
Ok here's a question, list the uses of ployesters.
synthestic or natural?

synthestic is terylene
natural are fat
fat as a polyester could be boiled with an alkali to form saop
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Offline idol2009

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Re: Chemistry Help HERE ONLY !!
« Reply #242 on: May 29, 2009, 11:15:12 am »
 Polyesters(such as terylene) are used mostly for clothing, they don't usually ask you for more than one use.

I also have another question: one one of the past papers (may/june 04, question 4) I was doing, there was a graph showing volume of aq.sodium hydroxide plotted against height of precipitate of iron (III) chloride. There is a upwards sloping line which flattens at 6 mm on the y-axis.
The question then asks you to sketch the graph that would be obtained if iron (III) chloride had been used. The mark scheme says it would be the same, except it would have a max of 8 mm, not 6
I don't really understand how you get that answer...why is the ppt.of iron (III) chloride taller than iron (II) chloride? i didn't even know there was a difference besides the color?

thanks if anyone can help!
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #243 on: May 29, 2009, 11:27:27 am »
Quote from: idol2009 on May 29, 2009, 11:15:12 am
Polyesters(such as terylene) are used mostly for clothing, they don't usually ask you for more than one use.

I also have another question: one one of the past papers (may/june 04, question 4) I was doing, there was a graph showing volume of aq.sodium hydroxide plotted against height of precipitate of iron (III) chloride. There is a upwards sloping line which flattens at 6 mm on the y-axis.
The question then asks you to sketch the graph that would be obtained if iron (III) chloride had been used. The mark scheme says it would be the same, except it would have a max of 8 mm, not 6
I don't really understand how you get that answer...why is the ppt.of iron (III) chloride taller than iron (II) chloride? i didn't even know there was a difference besides the color?

thanks if anyone can help!

if u look at b)i)
it gives u the ionic equation   Fe3+   +   3OH-     goes to      Fe(OH)3

                                  there is a ratio of 1:3 as te Fe has 1 ion and OH has 3 ions
so put Fe2+ instead of Fe3+

so ur new equation would be

Fe2+     +     2OH-     goes to         Fe(OH)2

    this one has a ratio 1:2

so if the first one has a ratio of 1:3 ends at 12cm3 of aqueous sodium hydroxide
then the ratio of 1:2 will end at 8 cuz 2+1= 3 so 2/3 * 12 = 8
thats why it ends at 8cm3 of aqueous sodium hydroxide
« Last Edit: May 29, 2009, 11:37:40 am by LilWayne »
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #244 on: May 29, 2009, 11:34:24 am »
also the height or ppt is the same at 6mm, but the volume of aqueous sodium hydroxide is different
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Offline ZeroZero82

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Re: Chemistry Help HERE ONLY !!
« Reply #245 on: May 29, 2009, 11:38:28 am »
What are the physical and chemical properties of transition metals?
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Offline idol2009

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Re: Chemistry Help HERE ONLY !!
« Reply #246 on: May 29, 2009, 11:40:26 am »
Oh ok, so the graph is exactly the same, except it flattens at 8 cm3?
Thanks a lot, none of my friends could answer that question!
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #247 on: May 29, 2009, 11:42:48 am »
Quote from: ZeroZero82 on May 29, 2009, 11:38:28 am
What are the physical and chemical properties of transition metals?

physical:
-hard
-strong
-*high densities
-*high melting and boiling points

chemical:
-not very reactive
-*compounds usually colored
-*metals and compounds of catalysts are usually used as catalysts

NOTE: *= the most important
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Offline ZeroZero82

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Re: Chemistry Help HERE ONLY !!
« Reply #248 on: May 29, 2009, 11:44:31 am »
What about conducting electricity?
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #249 on: May 29, 2009, 11:46:42 am »
Quote from: ZeroZero82 on May 29, 2009, 11:44:31 am
What about conducting electricity?

yeah they do conduct electricity cuz they are METALS
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #250 on: May 29, 2009, 11:47:48 am »
Quote from: idol2009 on May 29, 2009, 11:40:26 am
Oh ok, so the graph is exactly the same, except it flattens at 8 cm3?
Thanks a lot, none of my friends could answer that question!
yeah it flattens at 8 cm3, and ur welcome
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Offline ZeroZero82

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Re: Chemistry Help HERE ONLY !!
« Reply #251 on: May 29, 2009, 11:58:22 am »
Quote from: LilWayne on May 29, 2009, 11:46:42 am
Quote from: ZeroZero82 on May 29, 2009, 11:44:31 am
What about conducting electricity?

yeah they do conduct electricity cuz they are METALS
I meant in molten state, or in liquid state
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #252 on: May 29, 2009, 12:01:23 pm »
Quote from: ZeroZero82 on May 29, 2009, 11:58:22 am
Quote from: LilWayne on May 29, 2009, 11:46:42 am
Quote from: ZeroZero82 on May 29, 2009, 11:44:31 am
What about conducting electricity?

yeah they do conduct electricity cuz they are METALS
I meant in molten state, or in liquid state


i have a  question for u

do you find molten copper inside electrical cables??
« Last Edit: May 29, 2009, 12:03:48 pm by LilWayne »
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Offline ZeroZero82

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Re: Chemistry Help HERE ONLY !!
« Reply #253 on: May 29, 2009, 12:06:46 pm »
No.
My friend told me when it is molten it will have free electrons, which makes it conduct electricity...and as well as, when it's (aq). Is this true?
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #254 on: May 29, 2009, 12:08:08 pm »
Quote from: ZeroZero82 on May 29, 2009, 12:06:46 pm
No.
My friend told me when it is molten it will have free electrons, which makes it conduct electricity...and as well as, when it's (aq). Is this true?

thats wat metals are all about free moving electrons!!!
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