Rule A and B out.
C and D seems to have the same concentration, but look at the chemical formula for both chemicals.
C is NaOH but D is Zn(OH)₂
D will have double the amount of hydroxide ions, so D is the answer.

why A and B out?

Look at the proportions of volume against concentration.
The higher the volume, the lower the concentration of the chemical.
50cm3 of 2 mol dm-3 NH4OH becomes 25cm3 of 1 mol dm-3.
So...to simplify the details...
A. 25cm3 , 1 mol dm-3
B. 50cm3 , 1 mol dm-3
C. 10cm3 , 1 mol dm-3
D. 10cm3 , 1 mol dm-3

And we choose D as the concentration is double. [Due to (OH)2.]

Edit: Whoops, don't follow the above concept. Use mv/1000.

This post has been edited by fhNicK: Oct 26 2008, 11:14 PM

oh..understood

eh u sure not using mv/1000?

D,i guess....mv/1000

hello
i disagree on
the higher the volume the lower the concentration
i dont think that is true
the volume may decrease or increase but if the molarity(mol dm-3) is the same the concentration remains the same
what matters is the mole no.

concentration only decreases if you add distilled water

This post has been edited by Jojos: Oct 26 2008, 11:11 PM

Sorry for the wrong concept. Can't really remember what I learnt a year ago.
Anyway, follow the explanation stated above and use mv/1000 to find the answer.
Thanks for clarifying and sorry if I caused any confusion.

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 ]

---

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

Erm.. are you sure the decimal is that much? I only get numbers like 2 decimal places..

Her working is wrong.
I think she converted the volume's unit to dm³
yet still using mv/1000.

The reason mole = mv/1000
is because usually the volume of chemical used is in cm³ which will be needed to be converted into dm³
whereas molarity is moldm^-3.


So mv/1000 is actually m x v/1000

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

lolz u all spm students ? or got form 4s .

Let say that you are given an essay title "Acid rain". It is an open essay. (English 119C)

So, can I write about the formation of acid rain, with all the scientific term inside?


And another essay is describe a famous scientist and his contribution to the world.
Do the examiner concentrate on the background of all the scientists? Or just their contribution will do?

This post has been edited by macamtakada: Oct 27 2008, 07:08 AM

Oh nooo . The answer is D ? ;x

My chemistry is not that good after all and SPM is so near ;x

An aqueous solution of Q has a pH value of 1. Q may be
I 0.1 mol dm-3 hydrochloric acid
II 0.001 mol dm-3 sulphuric acid
III 0.1 mol dm-3 nitric acid
Iv 0.1 mol dm-3 ethanoic acid..

A. I and III
B. II and Iv
C. I,II and III
D. I, III and Iv
how how how?

This post has been edited by vick5821: Oct 27 2008, 08:35 AM

it's not IV for sure... and I is a must.

What's the options for the answer?

Like KingKong said.. IV should definitely be out since Carboxylic Acids are weak acids..

I and II should be in.. and since there's no answer for just I and II then I guess it's C?

ans is not that..

I think A gua