Yes, my friend. Please correct me if I'm wrong. Anyway, is that form 4 or form 5 topic?

Form 4 ..salt chapter

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Added on January 10, 2009, 8:46 pmHow about the other 2 questions?

This post has been edited by vick5821: Jan 10 2009, 08:46 PM

Q11:
I, II and III only.
Chloride ions will form insoluble precipitation with silver ions at ratio 1:1, so there would be excess of free silver ions in the solution

Q15:
B
Zn_(s) + 2HCl_(aq) ---> ZnCl₂ + H₂
1 mole of Zn react with 2 moles of HCl to give 1 mole of hydrogen gas.
1.3g of zinc is equal to 0.02 mole of zinc (1.3/65=0.02)
hence,
0.02 mole of Zn react with 0.04 mole of HCl to give 0.02 mole of hydrogen gas.
since,
1 mole of gas occupies24dm³
therefore,
0.02 mole of gas occupies 0.48dm³

lol..for Q15, i have constructed a wrong equation.I still dont understand Q11

11.
In this case, NaCl solution has excess substances of Na⁺ and Cl^-. After the reaction, NaNO₃ solution is produced.
The remaining solution contains Na⁺, Cl^- and NO₃^-.

15.
Zn + 2HCl --> ZnCl₂ + H₂
According to reaction, a mole of Zn produces a mole of H₂.
number of moles of Zn = number of moles of H₂
1.3/65 = x/24
x = 0.48dm³

This post has been edited by IamjustME: Jan 10 2009, 09:14 PM

No Cl-

Amount of:
Na⁺ - 20cm³ x 0.5mol dm^-3 = 0.01mol
Cl^- - 20cm³ x 0.5mol dm^-3 = 0.01mol
Ag⁺ - 20cm³ x 1.0mol dm^-3 = 0.02mol
NO₃⁺ - 20cm³ x 1.0mol dm^-3 = 0.02mol

As we know,
Ag⁺_(aq) + Cl^-_(aq) ---> AgCl_(s)
1 mole of silver ions will react with 1 mole of chloride ion to form 1 mole of precipitation of silver chloride.
Hence,
In the solution, there are excess of silver ion in the solution
Ag: 0.02mol
Cl: 0.01mol
amount of Ag used to form precipitation: 0.01mol, so 0.02mol(initial) - 0.01mol(used to form precipitation) = 0.01mol(left)
so, there are still 0.01 mol of silver ions in the solution.

Burn your book.

Sorry, I'm not feeling well today.

This post has been edited by IamjustME: Jan 10 2009, 09:21 PM

dude, wrong answer...
you will get AgCl precipitation. sodium nitrate is soluble salt, so it will exist as free ions in the solution

haha..thanks jiaxun.I have understood

glad to hear that. any question regarding chemistry can PM me the link to your question and i will try to answer

tmr I will have question somemore.tonight I tsudy first on rate of reaction

erm, what is the hardest chapter in form 5 syllabus?

shud i change to account stream ?

I can master account subjects really well although i more interested in science stream and I was in science class,but when i see the subject my kepala mabok kepayang edi

You can still consider studying in Science stream taking up Accounts subject.

it really angers me really

the preparation we do for spm is really not up to par with the actual spm paper

i believe many will agree when they first took last year's chemistry paper

it differs for each schools here, my friend and as for me, i totally disagree with you. my school is one of the best here in sarawak and the preparations the teachers gave us are actually above the par. that is why most of the students of our school find it quite easy. besides, it depends on the students themselves to do the preparations. you should have needed to expect for the worse and did more preparations.

Not only last year; every year's Chemistry paper.

Nope ... that wasn't the case of my students. They all happy to thank me for the prediction

can anyone tell me the formation of sperm and ovum? I dont understand that