then become temporary teacher or apply for maktab or choose education course in uni after this ..
u will not leave the school..LOL
which of the following solutions has the highest concentration of hydroxide ion?
A. 50 cm3 of 2 mol dm-3 aqueous ammonia
B. 50 cm3 of 1 mol dm-3 potassium hydroxide
C. 20cm3 of 2 mol dm-3 sodium hydroxide
D. 50cm3 of 5 mol dm-3 zinc hydroxide.

yea...just use MV/1000 to find the mol, then u will know..
always think to find the mol if u r given concentration and volume
then, u will be able to determine which one has the highest concentration of OH^-
A. 0.1
B. 0.05
C. 0.04
D. 0.25 [multiply 2 to the mol u find(0.25 beacuse it is Zn(OH)₂ ]

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Added on October 27, 2008, 12:23 amgeng, V3.. study smart yea
best of luck to all the SPM students here..

This post has been edited by nicoleycc: Oct 27 2008, 02:35 AM

sorry.. i made a BIG mistake..
thanks for the correction
yea, the reason of mole MV/1000 is
to change the given volume with cm³ to dm³

To find the number of moles of a solute is solution is
n=MV
where M is molarity (mol dm^-3)
V is volume of solution in dm³

This post has been edited by nicoleycc: Oct 27 2008, 02:44 AM

Erm, i think is D, correct?
because for A, we cant use reactive metal like Potassium to react with acid because explosion will happen.
for B, copper metal do not react with acid cos it is located lower than H in ECS.
for C, this is insoluble salt, must use double decomposition method(mix soluble salt contain cation and another soluble salt contain anion }
for D, Mg can react with nitric acid.
please correct me if im wrong.

This post has been edited by nicoleycc: Nov 1 2008, 12:27 PM

yes, for example
Mg + H₂SO₄ -> MgSO₄ + H₂
Mg located higher than H, then it can grab or "rampas" the SO₄ ^2- from H

while for Cu
Cu + H₂SO₄ -> no reaction
Cu is lower than H in ECS, it cant grab or "rampas" the SO₄ ^2- from H.

This post has been edited by nicoleycc: Nov 1 2008, 01:43 PM