TYS 'O' LVL chem questions

last SG · 2008-10-15T00:35:24+00:00

relax relax.just do ur paper, mind ur own business.don look left right centre, just focus.

Ah sian SG

what is ar

atomic mass of 1/12 of 12 carbon atom (isit)

UltimaOnline SG

eh 1pm liao leh. Go makan a good lunch and relax urself (think of someone u love and feel happy) till the exam starts.

if u don't makan, empty stomach, blood glucose level low, brain cannot function properly, u cannot perform at ur best.

go makan some nice lunch, and relax and be happy. the more relax and happy u are, the better u will score in the exam.

UltimaOnline SG

what is ar

atomic mass of 1/12 of 12 carbon atom (isit)

Biangz eh. Fundamentals like definitions don't do last minute work lah.

Relative Atomic Mass is the mass of an atom of (a particular isotope of) an element, relative to one-twelfth the mass of an atom of carbon-12.

Ah sian SG

i suddenly very nervous ahhaha

UltimaOnline SG

i suddenly very nervous ahhaha

Ok Ok, stop asking qns liao. Go makan, go relax. Enjoy urself, enjoy the exams, enjoy ur holidays.

(And next year come for my 'A' level tution.)

tinuviel07 SG

FYI, "the role of cryolite in the extraction of aluminium" is NOT "Catalyst".

It's role is actually rather complex, and in any case, is not in the 'O' level syllabus.

http://en.wikipedia.org/wiki/Hall-H%C3%A9roult_process

but for 'O' levels, they need to know that it helps lower the melting point of aluminium oxide, no?

UltimaOnline SG

but for 'O' levels, they need to know that it helps lower the melting point of aluminium oxide, no?

In old 'O' level syllabus yes. New 'O' level syllabus taken out liao.

Ah sian SG

i too nervous liao

i now

ar = sum of isotopic mass X percentage

UltimaOnline SG

i too nervous liao

i now

ar = sum of isotopic mass X percentage

In other words, a weighted average of the isotopes.

For instance, given that average molar mass of Cl is 35.5, and that there are 2 isotopes, Cl-35 and Cl-37, find the relative frequency of each isotope.

Solution :

(x/100)(35) + ((100-x)/100)(37) = 35.5

x = 75

Hence 75% of all chlorine atoms have a molar mass of 35g, and 25% of all chlorine atoms have a molar mass of 37g.

eagle SG

this one the answer given by my teacher last time

(a)
(i) They are elements with the same chemical properties and number of protons, but with different number of neutrons.

(ii) Uranium-235, ²³⁵₉₂U

(iii) ²³⁵UF₆ diffuses faster. This is because it has a smaller molecular mass than ²³⁸UF₆.

(b)
(i) The mixture of cryolite and aluminium oxide has a lower melting point than pure aluminium oxide.

(ii) Aluminium is very reactive; it is higher in the reactivity series than hydrogen. Thus, hydrogen ions will be preferably discharged, not aluminium.

tinuviel07 SG

In old 'O' level syllabus yes. New 'O' level syllabus taken out liao.

haha haven't been reading syllabus =x

damn sian man.. yesterday my student can't make my timing, i can't make his timing then today his paper 3.. think the mum want to kill me liao

Ah sian SG

good luck everyone

hahaha if can make it next year come back help

UltimaOnline SG

haha haven't been reading syllabus =x

damn sian man.. yesterday my student can't make my timing, i can't make his timing then today his paper 3.. think the mum want to kill me liao

Heh, but u got 1 advantage : next two months students holidaying, I next 2 months no business no income, but for u since u "tutor after work nia", u still got steady income.

But nvm, student holiday, i also holiday lor.

(but holiday without money... *sob* )

eagle SG

Heh, but u got 1 advantage : next two months students holidaying, I next 2 months no business no income, but for u since u "tutor after work nia", u still got steady income.

But nvm, student holiday, i also holiday lor.

(but holiday without money... *sob* )

me also tutor after work Dec is for year end AWS bonus time :D

Hoping to use this holiday to prepare a room to teach grp tuition... Any tips? How do you advertise your services and get students?

davidche SG

me leaving at 1.30

exams starts at 2.30

need to buy pencil lead.

UltimaOnline SG

me also tutor after work

Hoping to use this holiday to prepare a room to teach grp tuition... Any tips? How do you advertise your services and get students?

So Eagle is an physics engineer by (full-time) profession? Then give tuition after work somemore. Wah, ur income pockets must be fat fat one...

Two main ways to advertise :

- Pay publications (eg. magazines), but this is usually for tuition centers with higher advertising budget.

- (Do it urself, and/or pay other pple to) Give out flyers to students (either in uniform, or simply appropriate age group youngsters in civilian clothing), and into residential (eg. HDB, bungalow) letter boxes.

tinuviel07 SG

me also tutor after work Dec is for year end AWS bonus time :D

Hoping to use this holiday to prepare a room to teach grp tuition... Any tips? How do you advertise your services and get students?

mine is mostly thru flyers, liaising with other tuition centres and word-of-mouth

davidche SG

classfieds.

eagle SG

So Eagle is an physics engineer by (full-time) profession? Then give tuition after work somemore. Wah, ur income pockets must be fat fat one...

Two main ways to advertise :

- Pay publications (eg. magazines), but this is usually for tuition centers with higher advertising budget.

Me only fresh grad electrical engineer, or rather, test engineer, in charge of DRAM testing :(

mine is mostly thru flyers, liaising with other tuition centres and word-of-mouth

Hmmm.... Liase with other tuition centres not easy...

classfieds.

That's an idea as well... But usually hard to get noticed...

tinuviel07 SG

well that's true.. in my case was because the centre has been around for 5 years plus so slightly easier

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