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  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
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    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
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    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
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    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
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    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
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    • Australian girl shares 10 reasons why she loves to live in Singapore. She correctly points out that Singapore might be the only country in the entire world where you needn't fear for your life when walking alone at night. In fact, she says Singapore is the only country in the world (she's a globe trotter) in which, for the entire duration of her stay in Singapore, she has never once felt her life to be in danger, unlike in every other country in the world that she's been too.

      https://www.youtube.com/watch?v=43a1jtwaRHI

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    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
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    • She's only 36 years old this year, and earned approx $30k per month for the last 15 years. She should easily have enough money to retire for the rest of her life. It's ridiculous (and disrespectful to the majority of Singaporeans who earn an average of $2k a month) that she's feeling depressed now for being unemployed. Many more of such overpaid bankers complaining on Transitioning.org. The dichotomy is disgusting : genuinely dead-broke unemployed Singaporeans with family burdens, alongside undeservedly overpaid rich bankers recently retrenched, both groups crying for help alongside each other on Transitioning.org.

      http://www.transitioning.org/2016/02/18/36-year-old-banker-who-used-to-earn-300000-to-400000-per-annum-frustrated-at-labour-policies/

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    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
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    • SINGAPORE: The Ministry of Health (MOH), National Environment Agency (NEA), Agri-Food & Veterinary Authority of Singapore (AVA) and Singapore’s national water agency (PUB) are jointly investigating a surge of patients with gastroenteritis in the Owen Road area, they announced on Tuesday (May 24).

      As of May 23, more than 180 cases have been reported, the agencies said in a joint press release. Investigation into the possible source has not concluded; however, as a precautionary measure, NEA will close Pek Kio Market and Food Centre for a thorough cleaning and disinfection from May 25 and 26. The market will re-open on May 27. On May 19, MOH was alerted by a general practitioner at Owen Road that the clinic had seen an unusual increase in the number of cases of gastroenteritis since May 16. Further investigations found that other clinics in the area had experienced a similar increase. In all, more than 180 cases had sought medical treatment for symptoms such as diarrhoea, vomiting, fever and abdominal pain in the past week. The cases typically recovered within a few days. There were seven patients who are warded at Tan Tock Seng Hospital for observation. All of them are recovering well, the agencies said.

      NEA, MOH, AVA and PUB said they had commenced investigations into the cause immediately on May 19, including collecting food and environmental samples from food outlets in the Owen Road area, as well as interviewing affected cases and screening stool samples from the affected cases. Their investigations found that the majority of the cases stayed near or visited the Owen Road area.

      Many of them had also patronised the Pek Kio Market and Food Centre, although the investigations did not identify any specific food stall that could be the source of the reported cases.

      Stool samples collected from cases tested positive for Rotavirus, which causes gastric flu.

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
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    7,748 posts since May '05
    • Originally posted by Flying grenade:

      Yeah okay, i shall stop asking u about reagents and conditions, too many differing R&C

      Cs toh advanced study guide pg 308 indicated halogen of benzene involves halogen carriers and at room temp. But it's summary at pg 315 indicate it needs heat. 

      Cs toh wrote friedel crafts reactions require heat,  but the small hci book written by pang peng cheong wrote r.t.

      Nvm, I'll just write one of them in the exams 


      Generally, just follow trusted sources such as CS Toh, Chan Kim Seng & Jeanne Tan, George Chong. If there are any differences between these trusted authors, or even minor inconsistencies within each author, these differences are almost certainly going to be minor to the point of insignificance, and Cambridge will almost certainly accept all their (slightly differing) answers.

      Don't OCD about it lah. Be like me, lepak lepak, relak relak, anyhow do, anyhow write, anyhow skip, also get my A grade. *GuaiLanz LOL*

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • Originally posted by Flying grenade:

      Yeah okay, i shall stop asking u about reagents and conditions, too many differing R&C

      Cs toh advanced study guide pg 308 indicated halogen of benzene involves halogen carriers and at room temp. But it's summary at pg 315 indicate it needs heat. 

      Cs toh wrote friedel crafts reactions require heat,  but the small hci book written by pang peng cheong wrote r.t.

      Nvm, I'll just write one of them in the exams 


      Generally, just follow trusted sources such as CS Toh, Chan Kim Seng & Jeanne Tan, George Chong. If there are any differences between these trusted authors, or even minor inconsistencies within each author, these differences are almost certainly going to be minor to the point of insignificance, and Cambridge will almost certainly accept all their (slightly differing) answers.

      Don't OCD about it lah. Be like me, lepak lepak, relak relak, anyhow do, anyhow write, anyhow skip, also get my A grade. *GuaiLanz LOL*

      Edited by UltimaOnline 24 May `16, 9:27PM
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • Originally posted by Flying grenade:

      Pang cheng cheong's book and my school cher say reaction of carbonyl cpds with 2,4dnph is at r.t. , but cs toh book say heat, and making sense's reagent and conditions say need warm!

      How??? These reagents and conditions makes me damn f**king agitated!

      Idk but this is one of my thought 24dnph reaction(condensation/nu sub) can be carried out under r.t. But perhaps warm, accelerates the reaction , right? So both are acceptable. My doubt, would cambridge mark both correct?? If i write heat will they know cos i know the reaction will be quicker? Or will they think i am dumb , the reaction requires heat to overcome Ea of reaction? So write 24dnph, r.t. more safe is it?


      Allow BedokFunland JC to enlighten thee :

      As far as 2,4-DNPH is concerned, Cambridge doesn't give a flying f**k whether you write "room temperature" or "warm" or "heat" or even if you don't specify the temperature at all.

      However, don't mistake Cambridge's kind reasonable tolerance for weak bochup nonchalance : between PCl3 and PCl5, you *must* specify "heat" for 1 of these reagents, or Cambridge will penalize you. If Cambridge asks you to explain why this difference, do you know how to answer?

      (let's hope for more such out-of-the-box questions for this year's and all future Singapore H2 Chemistry papers, shall we? That will shut up those armchair critics who take perverse pleasure in criticizing the entire Singapore education system to be all about blind memorization without deeper understanding... such criticism applies more for PSLE, N and O levels, but less so for A levels and certainly not Uni levels; and among A level subjects, such criticism is even less valid for Chemistry than other A level subjects, hopefully Cambridge will continue this trend for Singapore's H2 Chemistry).

      Edited by UltimaOnline 24 May `16, 5:30PM
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • Originally posted by Flying grenade:

      One of my teacher  say that the reason why H- cannot reduce alkene is because alkene C=C bond is neutral(i.e. not polar)

      All along i was under this impression. 

      Today,  another different teacher say the reason is because the lone pair on H- repels with the pi e-cloud of C=C bond

      :/ i am flustered 


      See if you're intelligent enough to see how the following Singaporean link explains the answer to this H2 Chemistry question.

      http://mothership.sg/2016/05/wear-white-movement-to-be-held-on-the-same-day-as-pink-dot-yet-again/

      Whether you get it or not, don't post further on this topic on this forum, don't spoil the fun for others! *evil laugh*

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • Originally posted by Flying grenade:

      Why is Mno4- a stronger oxidising agent compared to Cr2O72-?


      Because of a complex combination of reasons, which you needn't worry about for A levels. Most relevantly, the oxidation state of the heteroatom in the oxidizing agent (ie. +7 versus +6), but also the electronegativity, the charge density, the electron affinity enthalpy, hydration enthalpy, electron configuration, reaction mechanism, etc.

      So when you explore these issues at Uni level, you'll realize there are no longer any short, simple answers (those are the O level days of naivety), but a beautifully complex balance of separate (and oftentimes opposing factors). A levels is a transition state or intermediate between naively simplistic O levels, and beautifully complex Uni levels.

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • Originally posted by Flying grenade:

      Pang cheng cheong's book and my school cher say reaction of carbonyl cpds with 2,4dnph is at r.t. , but cs toh book say heat, and making sense's reagent and conditions say need warm!

      How??? These reagents and conditions makes me damn f**king agitated!

      Idk but this is one of my thought 24dnph reaction(condensation/nu sub) can be carried out under r.t. But perhaps warm, accelerates the reaction , right? So both are acceptable. My doubt, would cambridge mark both correct?? If i write heat will they know cos i know the reaction will be quicker? Or will they think i am dumb , the reaction requires heat to overcome Ea of reaction? So write 24dnph, r.t. more safe is it?


      Allow BedokFunland JC to enlighten thee :

      As far as 2,4-DNPH is concerned, Cambridge doesn't give a flying f**k whether you write "room temperature" or "warm" or "heat" or even if you don't specify the temperature at all.

      However, don't mistake Cambridge's kind reasonable tolerance for weak bochup nonchalance : between PCl3 and PCl5, you *must* specify "heat" for 1 of these reagents, or Cambridge will penalize you. If Cambridge asks you to explain why this difference, do you know how to answer?

      (let's hope for more such out-of-the-box questions for this year's and all future Singapore H2 Chemistry papers, shall we? That will shut up those armchair critics who take perverse pleasure in criticizing the entire Singapore education system to be all about blind memorization without deeper understanding... such criticism applies more for PSLE, N and O levels, but less so for A levels and certainly not Uni levels; and among A level subjects, such criticism is even less valid for Chemistry than other A level subjects, hopefully Cambridge will continue this trend for Singapore's H2 Chemistry).

      Edited by UltimaOnline 24 May `16, 5:29PM
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • Originally posted by Flying grenade:

      One of my teacher  say that the reason why H- cannot reduce alkene is because alkene C=C bond is neutral(i.e. not polar)

      All along i was under this impression. 

      Today,  another different teacher say the reason is because the lone pair on H- repels with the pi e-cloud of C=C bond

      :/ i am flustered 


      See if you're intelligent enough to see how the following Singaporean link explains the answer to this H2 Chemistry question.

      http://mothership.sg/2016/05/wear-white-movement-to-be-held-on-the-same-day-as-pink-dot-yet-again/

      Whether you get it or not, don't post further on this topic on this forum, don't spoil the fun for others! *evil laugh*

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • Originally posted by Flying grenade:

      Why is Mno4- a stronger oxidising agent compared to Cr2O72-?


      Because of a complex combination of reasons, which you needn't worry about for A levels. Most relevantly, the oxidation state of the heteroatom in the oxidizing agent (ie. +7 versus +6), but also the electronegativity, the charge density, the electron affinity enthalpy, hydration enthalpy, electron configuration, reaction mechanism, etc.

      So when you explore these issues at Uni level, you'll realize there are no longer any short, simple answers (those are the O level days of naivety), but a beautifully complex balance of separate (and oftentimes opposing factors). A levels is a transition state or intermediate between naively simplistic O levels, and beautifully complex Uni levels.

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • Originally posted by Flying grenade:

      Hi ultima , i would like to ask,

      I have written down the kb value from the soln  book,

       

      I am confused by this part 

      In part i), the ka value is for phenylammonium cation, correct?

      For the part of vol base added = vol equivalence, i used kw/ka(phenylammonium) to get kb(phenylamine)

       

      So, when i use kw/ka is get kb of the cj base ah??

      Damnit, all the while i thought its ka and kb of the same molecule !

       

      When i apply kw/ka to find kb, is the kb the kb of same molecule or kb of its cj base!


      Ka of HA x Kb of A- = Kw

      Ka of BH+ x Kb of B = Kw

      Ka of conjugate acid x Kb of conjugate base = Kw

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • Originally posted by Flying grenade:

      Hi ultima , i would like to ask,

      I have written down the kb value from the soln  book,

       

      I am confused by this part 

      In part i), the ka value is for phenylammonium cation, correct?

      For the part of vol base added = vol equivalence, i used kw/ka(phenylammonium) to get kb(phenylamine)

       

      So, when i use kw/ka is get kb of the cj base ah??

      Damnit, all the while i thought its ka and kb of the same molecule !

       

      When i apply kw/ka to find kb, is the kb the kb of same molecule or kb of its cj base!


      Ka of HA x Kb of A- = Kw

      Ka of BH+ x Kb of B = Kw

      Ka of conjugate acid x Kb of conjugate base = Kw

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    7,748 posts since May '05
    • A man who wishes to remain anonymous took a selfie with a Darth Vader display at a Target in Australia; he and his kids love Star Wars. When he took the photo, he spoke to some children nearby and told them what he was doing, according to the Knox Leader. That's when the mother of the children saw the interaction, followed the man outside of the store, took a picture of him, and shared on Facebook what she thought had happened — a pedophile inappropriately speaking with her children and taking pictures.

      The Facebook post called the man a "creep" and detailed the actions the mother took to protect her children, including alerting the police and security at the store. Until deletion, the story had been shared over 20,000 times. After being told by his friends about the post and photo, the man went to the police and cleared his name — but not before receiving death threats and dealing with repercussions that affected his family and children. The mother, who also wishes to remain anonymous, has since deleted the post and apologized, but is now receiving death threats herself for sparking a mob against the man.

      http://www.popsugar.com/tech/Father-Accused-Being-Pedophile-After-Darth-Vader-Selfie-37458133