Originally posted by arkszhi:

Hello, I have a couple of chemistry questions. Hope I can get some answers before tomorrow's exams. Please kindly explain why the answer is such.

1. Which of the following would produce bubbles of gas at each electrode, when electrolysed using platinum electrodes?

a) Copper(II) sulphate solution

b) Silver nitrate solution

c) Lithium chloride solution

d) Molten potassium iodide

(Answer: C)

a) ions present is Cu2+ , H+, OH- and SO42-

Cu2+ is discharged instead of H+ as Cu is less reactive

OH- will be discharge hence O2 produced

b) ions present is Ag+, H+, NO3- and OH-

same Ag+ is  is discharged instead of H+ as Cu is less reactive

OH- will be discharge hence O2 produced

c) ions present Li+ , H+, Cl- and OH-

H+ is dicharged instead as Li is more reactive

OH- will be discharge hence O2 produced, Cl- will only be discharged is it is in high conc.

d) ion present K+ , I -

So no option, K and I2 discharged

 

2. A real gas deviates from ideal behaviour because the molecules in a real gas

i. have different speeds

ii. have a definite size

iii. are subject to intermolecular forces

a) 1,2, and 3 are correct

b) 1 and 2 only are correct

c) 2 and 3 only are correct

d) 1 only is correct

(Answer: C)

Ideal gas law assume that the molecules size is neglible and molecules does not interfer with each other so the IMF shd be minimise.

  

3) In an electrolysis experiment, the same quantity of electricity deposited 16g of copper and 54g of metal X (Ar = 108). What was the charge on the ion of metal, X?

a) +1

b) +2

c) +3

d) +4

(Answer: A)

 

16 g of Cu is 16/64 = 0.25 mol of Cu

we assume Cu2+ which is the most common is aq state

so 0.5 mol of electrons is involve

Since 54/108 = 0.5 mol of X is discharge

Hence charge is 1+

Thanks in advance!

 

1. Which of the following would produce bubbles of gas at each electrode, when electrolysed using platinum electrodes?

a) Copper(II) sulphate solution

b) Silver nitrate solution

c) Lithium chloride solution

d) Molten potassium iodide

(Answer: C)

a) ions present is Cu2+ , H+, OH- and SO42-

Cu2+ is discharged instead of H+ as Cu is less reactive

OH- will be discharge hence O2 produced

b) ions present is Ag+, H+, NO3- and OH-

same Ag+ is  is discharged instead of H+ as Cu is less reactive

OH- will be discharge hence O2 produced

c) ions present Li+ , H+, Cl- and OH-

H+ is dicharged instead as Li is more reactive

OH- will be discharge hence O2 produced, Cl- will only be discharged is it is in high conc.

d) ion present K+ , I -

So no option, K and I2 discharged

 

2. A real gas deviates from ideal behaviour because the molecules in a real gas

i. have different speeds

ii. have a definite size

iii. are subject to intermolecular forces

a) 1,2, and 3 are correct

b) 1 and 2 only are correct

c) 2 and 3 only are correct

d) 1 only is correct

(Answer: C)

Ideal gas law assume that the molecules size is neglible and molecules does not interfer with each other so the IMF shd be minimise.

  

3) In an electrolysis experiment, the same quantity of electricity deposited 16g of copper and 54g of metal X (Ar = 108). What was the charge on the ion of metal, X?

a) +1

b) +2

c) +3

d) +4

(Answer: A)

 

16 g of Cu is 16/64 = 0.25 mol of Cu

we assume Cu2+ which is the most common is aq state

so 0.5 mol of electrons is involve

Since 54/108 = 0.5 mol of X is discharge

Hence charge is 1+

 

 

 

Mary and Jean were going to a neighbourhood park 800m away from their house .

Mary walked at 40m/min and Jean cycled at 160m/min .At Halfway ,Jean stopped to talk to her friend .When Mary arrived at the park ,Jean was still 200m away .How long did Jean talk to her friend ?

Time for mary to finish the journey

= 800/40

=20 mins

 

At 400 marks jean time = 400/160

= 2.5 min

Jean need another 200/160 = 1.25 min to reach 600m

Total time of jean traveling

= 2+1.25

=3.25

 

Hence Jean talk for

= 20 – 3.25

= 16.75 min

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                   

 

 

 

 

 

o        The ratio of the number of girls to the number of boys in school W was 3:1

The ratio of the number of girls to the number of boys in school Y was 1:2

The total number of pupils in school Y was twice the total number of Pupils in school W .

Find the ratio of the number of boys in School W to the number of boys in School Y.

 

Wg: Wb = 3:1

Yg: Yb = 1: 2

Since Student Y is twice of student W

Hence Yg: Yb = 2: 4

Therfore Wb: Yb = 1:4

 

U can take up some course. There is a course know as Certified Financial Planner. Mainly to train people to be financial advisor, or salesman of financial instrument, depending on how you view it. Cant remember which sch teaching it. Btw what your backgroud??? How risk tolerance are you? Mean can you afford to lose money? Or i shd ask, how much money can you afford to lose? Basic rule, no risk no gain; minimise risk not eliminate it.

Havnt expire, but some will expire by august or end of the year.
Please help me to ask around, cos it will be a waste to throw away after they expire.
Willing to split into smaller portion also.
Or any confectionary will to do charity sale, can also donate to them.

Hi people, i have some baking ingredients to be given away. Hopefully to charitiable of Non-profit organisation.
Include ard 20kg of phoon huat pineapple paste and some flour and chocolate.
Buy to make cookie during CNY but did not manage to find time to do it.
Can deliver is need but oni fri afternoon/sat morning.
Please PM me if you need or you are aware who need them.
Thank

You need to upgrade yourself. CFA or some wealth mangement certification offer by singapore, easier to obtain. CFM or something

Blk 23 Sin Ming Rd
Veri reasonable, but veri pack. Only sell in the afternoon. From 11 plus till ard 3pm. Need to queue up to order but quene move quite fast.
Coffeshop also sell veri nice toast roti buns after 2 plus.

Hi,
Nt sure this is a correct forum, but think food lovers visit here, may get good recommendation.

I am looking for an commercial oven.
With top and bottom fire,
1 phase electrical supply,
to be use at home for time being,
is can double deck best, else would settle for single deck.

Saw some at certain shopping mall brownie shops, anyone working at these shops or any bakery can help? Thank

Originally posted by babymac13:
Referring to the expired thread below.

http://www.sgforums.com/?action=thread_display&thread_id=155842

Pls reveal all your recommendations there especially I have heard some good [b]western food there.

[/b]

Blk 8 at lorong 7.
Closed on fri
Closed ard 9 plus.
Hainanese chef

Originally posted by dark_snowboy:

x- 600/(600/x + 220) =5.5

5.5-x = -600/ { (600+220x)/ x }

5.5-x = -600/ { (600+220x)/ x }

5.5-x = -600x/(600+220x)

(5.5-x) (600+220x) = -600x

(5.5-x)(60+22x) = -60x

330 + 121x -60x -22x(square) =-60x

-22x(square) +121x + 330=0

2x(square) - 11x - 30 = 0

Correct
(2x-15)(x+2) = 0
x = 7.5 hr
Spped of car =600/7.5 =80
speed 0f plane = 300
time for plane = 600/300 = 2hr
difference = 7.5 - 2 = 5.5 hr

There you go

Hei, have gather some of the topics that come out this morning. And think these other topics may be out for paper 2. No promise though. Free free to chip in ur comments. Correct me if wrong coz gather infor from students. After SS all tend to forget.

Will try to do one for A math. But need all ur helps

Topics that was out
a) Vector
b) Loci
c) basic Transformation

Topics that may be out for Paper 2:
a) Mensuratipn
b) 3 D Trigo
c) Number Pattern
d) Graph
e) Transformation (shear and stretch)
f) quadratic equation
g) Cumulative Frequancy Histrogram
h) interest, Discount

I need a classroom to do group tuition.
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Level: Seconadry 1 ~ 4
Able to sit ard 12 Secondary students.
Area ard Hougang, toa payoh, AMK
HP 9768 9626
Thank you

Want to be auditor must have accounting background. Go study ACCA
Want to be accountant you do not need although it is good to have auditing background.
Auditor more pay better career prospect but more stressful.

It is easier for JC study to upgarde as it is general eductaion. You can do fiance or acc or business mgmt etc. or even engineering.

For poly, coz it a specilaise eductaion, students may not upgrade as it may not be esay to find a similar field higher education. to switch major to alot of people is tough as it may be view as you have wasted your poly year.

Personally i think company would have a better career path for those who are versatile. JC students more versatile not because they are but becoz they have no specialisation. Pros and cons.

Anyone want to exchange papers?
Maths and Sciences - Preferable with Solution
Please PM
Lower Level are welcome 2.
Thank.

What is the surname name of Zhang Fei's (3 kingdom) Mother?

Ans: Wu: coz Wu Shi Sheng Fei

Originally posted by jayellefull:

im in sec four taking o levels this year too. interested in exchanging papers. so how's the deal?

I pass you the papers, you share with me your school papers or you help me with the answer schemes. That it.

Sorrie aint chio bu

i have both pure and combine

Do you want to exchange practice papers?

I have maths science and POA
Some have answer some dont
Interested please PM me.
Cheers!!!!!!!

Originally posted by Honeybunz:

I feel this way once a month and it lasts for days. I know many girls experience or claim to have that too.

But I feel that I cannot carry on like that every month. I hold back my temper so as not to affect anyone around me. But it doesn't change my mood. The more I hold back (by not scolding or yelling at ppl), the more I feel like a volcano trying to erupt but cannot erupt.

How ah?

Will exercise really help or not? I used to exercise. Didn't seem to improve. Or shall I do more strenous exercise to wear myself out, then I will feel less moody?

Any advise????

Dun noe whether you are mood swing due to PMS or other reasons.
If PMS then maybe you can show a bit of anger especially to your close friend , i think you are entitled to that. I dun think ppls would mind, girls would understand guy just have to bear with it.
Some guy r less sensitive then you may want tell them straight, that how i learnt from my friends. New quite sensitive, as long as a girl is pulling a face, i back up unless it last more than 2 weeks.

I know some guy also have periodical mood swing, NT PMS cos may nt be monthly, but may be cos it the time / date when they break up, or something else. If you are feeling down becoz of this reason, one way is to vent it out. Crying, MIA or anything

When it happen to me, I go acarde to play game or drive. Release stress.

Hello, I am looking for a place which i could sell stickers to children. Just need abt a 3X3 table size. Willing to share with people. Trying to be enterprising, sticker are my own source.
Can sms me at 9768 9626
Thank.

From the way I look at it, either he has no confidence in the relationship and dont wish to contiune or he may be in some trouble and dont want to make you suffer.

May be you should consider asking these questions:
Does he show signs of two timing you?
(pai sei the signs i am not veri sure)

On the bright side:
Does he really have problems with his work or business?
If yes, if there any ways you are able to help him to resolve the problems.
Help him to establish his business or give him the assurance that you will stick wif him.
I know a gal whom tell her husband that she will take care of their household expenditures while he quit his 3k job to start up his business, but of course she can manage as she also earn ard 3 to 4k a month.

Maybe he is feeling stress with the problems in his business.

Hope everything turns out fine.

I am looking for O and A level textbk and notes. Sciences and Maths and POA. Able to collect from your place. Kindly PM or sms me 9768 9626. Kindly list your sch for notes, textbook titles. Are willing to pay a small amount as token, please quote the amount. Thank

Dun know shd post here or market place. Here got more actitivies so decide to take a bet.

I am looking for O and A level textbk and notes. Sciences and Maths and POA. Able to collect from your place. Kindly PM or sms me 9768 9626. Kindly list your sch for notes, textbook titles. Are willing to pay a small amount as token, please quote the amount. Thank