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CHEM AND BIO HELP AND TIPS HERE

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@d!_†oX!©:

--- Quote from: Ari Ben Canaan on December 29, 2009, 07:21:58 am ---IGCSE Paper 3 Question 4 (b) (ii)

It says draw the new graph. How do u know where to draw the graph till. In the ms it says it should be drawn till 8cm3. How do u obtain this value and why this value ?

Help and plz explain well !!

--- End quote ---
Hey ari!!
could you also specify the year??

holtadit:
woops... 2004 may jun

I simply dont get it at all

Ghost Of Highbury:
this q irritated me a lot during my IGs

heres it..

first--> remember to use mole ratio in these types of Qs

the no. of moles of hydroxide ions => moles = conc. * vol = 1 * 12/1000 (i took 12 because at 12cm^3 in the x-axis the graph becomes constant, meaning anything further is an excess) = 0.012

the no. of moles of chloride ions = 1* 4/1000 = 0.004

mole ratio : 0.004:0.012 = 1:3

---------------------
Fe2+ + 2OH- = Fe(OH)2

from the above , u know that the mole ratio is 1:2

4.0 cm3 of aqueous iron(II) chloride = 0.004 dm^3

no. of moles of chloride ions = 1 * 0.004 = 0.004 moles
let the no. of moles of hydroxide ions be 'x'

therefore, 1:2 :: 0.004 : x

x = 0.008 moles of hydroxide ions

volume = moles/conc. = 0.008/1 = 0.008dm3 = 8cm3

so the shape shud be the same but it shud go constant at 8cm^3

holtadit:

--- Quote ---orry for taking so long...some important calls
Anyway

Na3PO4+ nTx(NO3)y----> NaNO3+ Thanks(PO4)z

all the variables are unknown at present

U know the reaction will give sodium nitrate which has the formula NaNO3[/sub]....now u also know the volume of the product is 8cm3
the volume of sodium phosphate is 2cm3...
The mole ratio of sodium phosphate and Tnitrate is 2:3, when u try to balance for NaNO3...and u get (NO3)2. The product side has 6NaNO3
This gives us the charge on T as +2...since (NO3)2-...u know PO4 will be twice and thus T will be thrice cuz of the charges
 
Little weird to understand...ill put down the balanced equation, which is likely to make it easy for u to figure it out

2 Na3PO4+ 3 T(NO3)2---->6NaNO3+ T3(PO4)2

I'll try explaining again...i tried my best to explain tho...
--- End quote ---

nid, im sorry i still dont get it.. :-[

Saladin:
The ansa is attatched.

Hope this helps.

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