O Levels almost over

Hi all students,

Both Maths papers are over! I think there is left with 1 MCQ Chemistry & for folks who are taking Biology as well.

With O Levels coming to an end, this blog WILL continue hee.... I appreciate all Sec 4s to pass on this blog to your juniors or even better still would be you putting a link www.askalwayslovely.blogspot.com on your blog. We have an enjoyable time answering and posting questions. Both Sean and me simply love it when we see students participating, leaving comments, answers. Simply awesome!

We will continue to reach out to all Sec 3 & 4 students especially those taking A/E Maths & Chemistry.

Oh yar! Both Sean and me are going to launch something in a months' time. It's going to be beneficial to those who are looking for tips, strategies to do well and to like the subject.

Meanwhile, keep in contact. If anyone of you need any help, send an email to askalwayslovely@gmail.com

Cheers
alwaysLovely & Sean

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O Level Chemistry Tip By Sean Out in 2007 Chemistry Paper 2

1 comments: illuminate-x said...
THANK YOU SO MUCH for the tip for the weak/strong acid question! It came out for Chem Paper 2 today and I was so relieved I saw the post just yesterday. :)

October 24, 2007 3:37 AM

WOW!

Chemistry Question - Metals & Gases

Hi, I have a Chemistry question..

A metallic element, M, has the following properties:
less dense than water
soft
melts below 100C
occurs naturally as its chloride, formula MCl
the oxide of M reacts with water to form a solube hydroxide

Suggest how metal M can be extracted from its compounds. Explain your reasoning.

Also, how do I distinguish between hydrogen gas and nitrogen gas?

1st step is to identify the reactivity of this metal in order to check out the extraction method of these metals from its compounds (etc, their ores or chlorides)
The properties given suggest clearly that it belongs to Group 1 of the periodic table.

For Group 1 Alkali Metals, they are classified as the most reactive metals/elements.
You should already know about the metal reactivity series by now.

For these reactive metals, the compounds they formed are known to be unreactive (or stable).
Yes. Reactive Metals will formed Stable Compounds!

As such, for these Unreactive Compounds, the only way to extract the pure Metals is by electrolysis of their salts/compounds in aqueous (water) or in molten state.

Hope this information helps.

PS: For the N2 and H2 gases, i am not sure what you mean. But it you really want to differentiate N2 and H2 in the lab, you canm just test for the POP sound with a lighted splint.

Sean
SimpleChemConcepts
Learning Experience With A Difference

Chemistry Question - Acids,Bases & Salts, Organic Chem

Question:

Q1) desribe an expt that you wld caryy out t show that sulphuric acid is a strong acid but ethanoic acid is a weak acid

Ans: This is testing you on the properties of acid. There are 4 ways for you to differentiate acid - pH paper test, Reaction w Metal, Reaction with Carbonate or Reaction with an Alkali. To differentiate the acidity of Sulphuric Acid and Ethanoic Acid, i would suggest to test the amount of CO2 Gas produced when certain amount of the acid are reacted with a certain mass of say calcium carbonate. Suphuric Acid, being stronger acid will tends to give off CO2 gas more and at a faster rate.

Q2)2 salts formed frm sodium hydroxide and phosphoric acid other than NaH(2)PO(4.

Ans: Phosphoric Acid is TRIBASIC, meaning it has 3 Hydrogen atoms to dissociate. It will form 3 salts when reacted with NaOH.

H3PO4 -> 3H+ + PO4^3-
H3PO4 -> 2H+ + HPO4^2-
H3PO4 -> 1H+ + H2PO4-

NaOH + H3PO4 -> Na3PO4 (Ans) + H20
NaOH + H3PO4 -> Na2HPO4 (Ans) + H20
NaOH + H3PO4 -> NaH2PO4 + H20

PS: Pls not equestion is not balanced yet.

Q3) explain why NaH(2)PO(4) is both an acid and a salt.
Ans: It is an acid bcos it can dissociates H+ in water making the solution acidic.
It is a salt bcos it is made by the neutralization process of NaOH and H3PO4. Anyhow, it can also be made by the reaction of H3PO4 with Na metal or NaCO3.

Q4) structural formula f repeat unit of styrene-butadiene
Ans: This should not be covered in GCE O level syllabus. Learnt this poly/uni.
You should know the structural formulae of Styrene monomer, but the question should give you the structural formulae of butadiene. With those structures, use the theory of Addition Polymerization.

All The Best!
Sean
SimpleChemConcepts
Learning Experience with A Difference

Final Preparation - Stay Focused!

One more day and your O Level examinations will be kicked-start formally..

Understand that some are feeling tired and some bored after preparing for the Prelims, taken it and now another period of preparing for your O levels.

Come on! Cheer up! We have been through all this before..You are not walking alone..

Stay Focused and Determined..Just 1-2 more weeks...

If you happen to be still able to see this blog, check out the short video clip:
http://successessentials.blogspot.com/2007/07/inspiring-movies-most-influential.html

Last but not least,i would like to wish you:

ALL THE BEST TO YOUR COMING EXAMS!!!!

=)

Sean
SimpleChemConcepts
"Learning Experience with A Difference"

A qn from June 2007 Qn Coordinate Geometry

Point B is intersection of Line AE & BE
1.find eqn of these 2 lines
2.Solve simultaneously
B= (5,8)


Area of EBC is given
Never use distance to solve this part!

1/2 xBxH = 24
What's the base? What's the height?
Base = EC = (x-3)
Height = Vertical Distance from B to line EC = 4

By simply using the CORRECT base & height strategy allows me more time for the rest of the questions!

C=(15,4)

To find D,
Use Eqn of AD

D=(15,-2)

;)

More elaborate step by step solutions & power tips are
available here.
Click here
We have parents
already purchased a copy for their children. Even students buying for themselves
through Bank Transfer.
I was "scolded" by one of the students who bought the
papers "Why didn't you let me know earlier?"
Well, late better than never,
isn't it? ;)

Well, there's only 1 O level and it's really starting. You
decide how you want to spend your time.
For those who are serious in doing
your best and getting the marks you deserve for your Monday paper, you
should get the step by step solutions today cos price is going up tm(Fri)

What another student did for this qn:
(Click on the image to see clearly)

June 2007 A-Math Paper Step by Step Solutions

Dear students,

Those who have completed your June 2007 Papers! Well Done!

I can't provide the solutions for free as there are already some students who have bought the step by step solutions & Power Tips for June 2007. I need to be fair to them.

Btw, I have received email from a student that I should not be giving out the June papers free as some of you paid $1 for it.

But the ironic is. though I'm giving it for free, only a handful of serious students are downloading and taking actions to do and find out the areas they can improve on.

For those who wants to check the answers, you can perhaps discuss with your friends or you can get your copy of the step by step solutions here
>> Strategies to solve the latest O Level Questions Trends Quickly & Easily
>> http://www.singaporeolevelmaths.com/squaringexpert.html for Maths Strategies

I have provided a tip and answer for June 07 P2 Q12 Co-ordinate geometry qn here
>> http://askalwayslovely.blogspot.com/2007/10/qn-from-june-2007-qn-coordinate.html

All the way!

Chemistry Questions - Separation / Gases

Q)Which gas is produced in large quantities by fractional distillation?
A. chlorine
B. ammonia
C. nitrogen
D. methane

Last question for the night. Come on..Students taking your Chemistry Paper 2 on next Wednesday. Time for you to answer this question.

Rgds
Sean
SimpleChemConcepts
Learnig Experience with A Difference

Chemistry Questions - Energy Changes

Q)When solid potassium chloride is added to water, the temperature of the mixture falls. What conclusion can be made from this observation?
A. The process is endothermic.
B. The process is exothermic.
C. All solids dissolve with a fall in temperature.
D. Very little potassium chloride dissolves in water.

Anyone would like to share your answers for above Energy Changes questions?

Rgds
Sean
SimpleChemConcepts
Learning Experience with A Difference

Chemistry Questions - Bonding

Q)Which pair of substances is most suitable for the preparation of copper(II) sulphate?
A. Aqueous copper(II) nitrate and aqueous sodium sulphate
B. Copper(II) carbonate and dilute sulphuric acid
C. Copper and dilute sulphuric acid
D. Copper(II) oxide and ammonium sulphate

Takers??

Rgds
Sean
SimpleChemConcepts
Learning Experience with A Difference

Chemistry Questions - Mole Concepts

A Chemistry Question that was posed by a local singapore student that is taking her O level this year.

Which of the following consists of the greatest number of atoms?
A. 4g of hydrogen gas, H2
B. 48g of solid magnesium, Mg
C. 71g of chlorine has, Cl2
D. 24 dm3 of argon gas, Ar at r.t.p.

Any takers??

Rgds
Sean
SimpleChemComcepts
Learning Experience with A Difference

June 2007 A-Math Paper gives you An unfair advantage over your friends

For all taking A-Math :

This is the only paper you MUST complete before 22nd Oct.

All A-Math students must complete and learn from any mistake that you have made from June 2007 Papers. Y
ou must have at least 30 minutes to check otherwise you are either not managing your time to the optimum or you are using a longer strategy.

By doing so, it gears you up for the big thing and brings you closer to what you want to achieve.

Those whose do not have the Papers, download the papers for free, just a click away! Do it quietly and fastly!

>>http://www.singaporeolevelmaths.com

Almost 30 students have downloaded it! Get yours too!

The BIG THING is starting!!!

You can do it!

For those who have completed the papers, do you want to find out how to complete the papers leaving you time to check, double check, triple check?

Chemistry Questions - Bonding

Here is another one for you to be exposed to:

Q) Which of the following compounds has the largest number of lone pairs of electrons on the central atom?

A) CCl4
B) NH3
C) CO2
D) H2O

Share your thoughts with us.

Rgds
Sean
SimpleChemConcepts

Chemistry Question - Redox

Halo, Try this one...

Q) A drop of solution S turns acidified orange potassium dichromate (VI) to green chromium (III) ions. What must solution S contain?

A) An acid
B) An oxidizing agent
C) A reducing agent
D) A substance that can be oxidized

Come on students....

Rgds
Sean
SimpleChemConcepts

Chemistry Question - Macromolecule

Q)Fat and Terylene are:

A) Natural polymers
B) Polyamides
C) Polyesters
D) Synthetic polymers

Try it out!

Rgds,
Sean
SimpleChemConcepts
"Learning Experience with A Difference"

Chemistry Question - Acids/Bases

Q) Which of the following statements is true of the hydroxide ion?

A)It is a product of reaction btw hydrogen and oxygen
B)It is present in aqueous ammonia
C)It is present in pure alcohol
D)It is present in pure water

Show your explainations.

Rgds,
Sean
SimpleChemConcepts
"Learning Experience with A Difference"

Chemistry Question - Periodic Table

Question from a Top School 2007 Prelim Paper:

Q) Astatine is a Group VII element below Iodine in Periodic Table. Which of the followingf statements concerning Astatine is correct?

A) It is a liquid at room temp and pressure.
B) It is a stronger oxidizing agent than iodine
C) It reacts with sodium ti form an ionic compound
D) Its diatomic molecules are held together by weak covalent bonds

Should be a mangeable question. Enjoy doing!

Rgds
Sean
SimpleChemConcepts
Learning Experience with A Difference

Chemistry Question - Metals / Periodic Table

Halo Students,

Chem Practical is round the corner and Chem Paper 2 in less than 3 week time.
Hope your preparation is going well.

Since this is the weekend, i think you might want somemore conceptual chem questions to think it through. Here is the start of more to share:

Q)Calcium Carbonate decomposes more readiliy on heating than sodium carbonate. Suggest a reason for this.

CaCO3 --> CaO + CO2
Na2CO3 --> Na2O + CO2

Think about it.

Rgds
Sean
SimpleChemConcepts
"Learning Experience with A Difference"

A-Math Circular Measure

5 marks, showing qn.

:)

Take a break!

MAGIC #1>>>>>>>>
An Indian discovered that nobody can create a FOLDER anywhere on>>>> the>>>> computer which can be named as 'CON'. This is something pretty>>>> cool...and unbelievable... At Microsoft the whole Team, couldn't>>>> answer why this happened!>>>> TRY IT NOW ,IT WILL NOT CREATE ' CON ' FOLDER>>>>>>>>>>>>



MAGIC #2>>>> For those of you using Windows, do the following:>>>>>>>>
1.) Open an empty notepad file>>>>
2.) Type 'Bush hid the facts' (without the quotes)>>>>
3.) Save it as whatever you want.>>>>
4.) Close it, and re-open it.>>>>>>>> is it just a really weird bug? :-??>>>>>>>>>>>>




MAGIC #3>>>> microsoft crazy facts>>>>>>>>>>>> This is something pretty cool and neat...and unbelievable... At>>>> Microsoft the whole Team, including Bill Gates, couldn't answer>>>> why>>>> this happened!>>>>>>>> It was discovered by a Brazilian. Try it out yourself...>>>>>>>> Open Microsoft Word and type>>>>>>>> =rand (200, 99)>>>>>>>> And then press ENTER>>>> then see the magic...............................

Chemistry Question

what would happen if damp(moist) iron ore were placed in the blast furnace?


Can the student that post this question share with us how you got this question and perphaps share some light on the answer (if any). Moist Iron Ore might not necessarily react with the CO.

Chemistry Questions - Mole Concepts

Try this Mole Concepts O Level Chem questions:

Q) If 2g of hydrogen gas contains x molecules, how many molecules would 2g of nitrogen gas contain?

A) x
B) 7x
C) x/14
D) x/28

Show me the working briefly on how you derive your answer. This way we can determine your concepts for this chapter.

Rgds
Sean
SimpleChemConcepts

Qn answered under comments

Chemistry Questions - Organic Chemistry

Halo,

Came across the following question with my student today and thought you will be interested to give it a try:

Q) Which statement is true for both propene and polypropene?
A) They have identical empirical formulae
B) They are insoluble in organic solvents
C) They have identical molecular formulae
D) They decolourise liquid bromine solution rapidly

Come on O Level students, give it a shot.I understand that lots of you are checking out on this blog. The best way to learn is to Just Do It (like NIKE)! Nothing to be shy about, just share your answer. It is alright if you got it wrong. Failure is the mother of success, still rmbr that?

PS: Thank you "C" for letting me this chance to share the above question.

Cheers
Sean
SimpleChemConcepts

Qn answered and explained under comments

A-Math Integration of tan^2 x

lijun(: said...
i came across this qu that day, and i really want to clarify if the method i used is correct or not.

int(tan^2x - x^3)

i changed it to int(sec^2x - 1 - x^3) instead, cos i don't think we can integrate tan.

is that feasible?

Absolutely. Since tan^2 x can't be integrated, you must think of alternative by making use of the relationship of tan^2 x + 1 = sec^2 x

A-Math P & C Clarification

lijun(: said...
hey. i just want to clarify something that i'm not very sure of.

is nCr x r! = nPr ??


By definition,

nCr = nPr/r!

Well, I never remember this 'rule'
For example, find the number of ways to form a 3 letter word from a,b,c,d,e

Student #1:
5C1*4C1*3C1

Student #2:
5P3

Both answers are correct though different approaches are taken, so no need to remember the 'rule'

:)

Chemistry Questions - Bonding / Organic Chemistry

Hey students,

Try this O Level Chemistry questions on Bonding and Organic Chemistry.

Q) The number of shared pairs electrons in a molecule of methanol is:
A) 3
B) 4
C) 5
D) 6

Show me your reasoning.

Rgds,
Sean
SimpleChemConcepts

Qn answered and explained under comments

Excellent Positive Attitude

Think i came in bit late, but better than never i suppose..Happy Childrens Day!

You have been working very hard (i suppose) for the past few months. Regardless of the results that you achieved in your Prelims Exams, Give Yourself some "Claps"..You deserve it more than anyone, for working so hard.

Been too stressup to even give yourself a SMILE =)??
Check this Thai Ad out...You do need to take some time off to chill and refresh your mind..while studying for the finale.


Nice rite?? Hope i can see you smiling.

There are some who told me that they have problem to keep focus and prepare for their upcoming O levels. I would just like to urge you to stay positive during this period. Think of the dream college/Poly Course that you would like to go..Think of the fun and the amount of things that you are going to do when you finish of your last paper..and you could simply put down that rock on your chest, by simple saying: "Yes. I have finally done my part for the O levels. Nothing to regret at all. Time to enjoy!"

Here is one of those movies that i watched regularly to stay motivated and positive.
Hope you will find it equally Inspiring.


Rgds,
Sean
SimpleChemConcepts

Great Partcipation Going On!

hello Big Children!
Happy Children Day! ( I almost type Happy Chinese New Year!) tsktsk
I believe all of you have received your prelim results by now.

Those who have done well, continue with the good progress. Remember, you have completed the entire race only when you touch the finishing line ( Recall: the hare and tortoise story) Lend a hand to friends who need a little support and a little encouragement :)

For those who didn't do as well, now is the final chance, you are given 1 last chance, you either make the best out of it or ....... well, there's NO or!
You only have 1 option : Run this race as hard as you can to finish this race! Even with panting breath, tired legs, sore feet...... You must do it!

Me and Sean will be here to lend you all the support you need for the next 30days or so!

All the way!

“When things go wrong, as they sometimes will,
When the road you are trudging seems all uphill,
When the funds are low and the debts are high,
When you want to smile but you have to sigh,
When care is pressing you down a little bit,
Rest, if you must - but don’t you quit!

Life is queer with its twists and turns,
As everyone of us sometimes learns,
And many a failure turns about
When he might have won had he stuck it out;
Don’t give up, though the pace seems slow
You must succeed with another blow.

Success is a failure turned inside out
The silver tint of the clouds of doubt
And you can never tell how close you are,
It may be near when it seems afar;
So stick to the fight when you are hardest hit
It’s when things get worse you mustn’t quit.” Edgar Guest

I listen to this when I need to run my own races :)