STPM Chemistry

[adrianng]

Hi, come across this forum and noticed a lot of STPM candidates in this site. I am a tuition teacher for STPM chemistry in Penang. Start this forum to help those who need advise on STPM chemistry. Feel free to ask, i will try to answer your question when i am free.

[winson227]

hw we recognise the organic chemical formula effectively??? i will easily 4get all the formula after exam or afew days after i had read the chapter........

[kaiyi]

Summarise them - write your own notes about the general formulas eg alcohol hydration...Use 15 minutes to view through all the formulas (or at least half) everyday. Don't spend too much time on it. just consistently read it and they'll be in your head!

[Sola]

The best way is to do questions on organic!!There is no better way than answering question and recalling what u had learn~For me,organic chemistry is jus like a game,u play it,u rmb it

[markwongsk]

Yea I agree with you. It's more like a detective game, where you're given a specific reagent and substrate and you have to predict the product, or you're given the observations and you have to deduce what happened. You just have to do a lot of practice.

[Athersin]

Hi! A question here to ask

what is the composition of 0.1M sodium acetate buffer pH 5.00? (ratio of ch3coo-:ch3cooh), acetic acid has pka of 4.76.

i get a ratio of 1.74. ( Should be correct)
but when it comes to the question below:
write direction for making 1L of the buffer described above with ch3cooh(0.2M) and ch3cooNa (0.2M).
i get a little bit confused.
Any Help is much appreciated.

[adrianng]

hi Athersin,
you have to find the mole of the ch3cooh and ch3cooNa in 1L (eg: 0.2M x 1L). After that times with the molar mass of each to find the mass needed and later top up with dH2O to 1L.

As for organic formulae, the most important thing is you know what is the functional group for each homologue series, so if you forgot the formulae, just draw out the carbon skeleton and substituted in the functional group, the rest fill with hydrogen, then you can count how many carbon, hydrogen and so on atom to find the molecular formulae. Of course, the best way is to memorize all. Try draw a table and list down all the formulae, i can help if you need one.

[plouffle]

1）which of the following elements wlll not form both ionic and covalent compounds?
ANSWER IS sodium。WHY？IT CANNOT FORM covalent bond？BUT WHY NAOH CAN form?
（OXFORD ACE AHEAD CHAPTER 6 EXAM PRACTISE QUESTION 1，PAGE 175）

2）
ANSWER IS A，RIGHT？