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ZeroZero82:
Ok here's a question, list the uses of ployesters.

unknown 101:

--- Quote from: ZeroZero82 on May 29, 2009, 11:04:16 am ---Ok here's a question, list the uses of ployesters.

--- End quote ---
synthestic or natural?

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

idol2009:
 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!

unknown 101:

--- 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!

--- End quote ---

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

unknown 101:
also the height or ppt is the same at 6mm, but the volume of aqueous sodium hydroxide is different

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