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 SPM Thread 08/09 (V 3), SPM is coming soon..!!!! Final days..!!

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neorelated4
post Nov 1 2008, 03:53 PM

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QUOTE(DXK @ Nov 1 2008, 02:45 PM)
Hi guys I got a Q I wanna ask, hope u can help

Which of the following pairs of substances is most suitable to prepare copper(II) sulphate
salt?

A. Copper with dilute sulphuric acid
B. Copper(II) chloride with dilute sulphuric acid
C. Copper(II) carbonate with dilute sulphuric acid
D. Copper(II) nitrate solution with sodium sulphate solution
*
CuSO4 is soluble salt. D is definitely not possible.. this is no double decompostition reaction.
A is not possible because Hydrogen is more reactive than copper metal.
I would choose C.

to get CuSO4 there are 3 ways. copper oxide with sulphuric acid, copper hydroxide with sulphuric acid or copper carbonate with sulphuric acid.
neorelated4
post Nov 1 2008, 06:38 PM

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it's not. if it were then a precipitate would form. double decomposition reaction only occurs when 2 soluble salt solutions are mixed together and an insoluble salt is formed. since cuso42 is soluble, hence no precipitate will form.
neorelated4
post Nov 4 2008, 12:20 PM

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QUOTE(aad_lfcfn @ Nov 4 2008, 04:36 AM)
how to count the number of chromosome on certain mitotic or meiotic phase?

(Question asked in Biology Paper 1)
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in a diagram if they ask you how many chromosomes are there. just count them by the centromeres. don't need to look at whether they are diploid or haploid or whatsoever. 1 centromere=1 chromosome regardless at what stage.
neorelated4
post Nov 8 2008, 11:03 PM

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initial reactant is lead(II) nitrate salt. only lead OXIDE is brown when hot yellow when cold. only zinc OXIDE is yellow when hot white when cold.
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