hkdse chem practice paper Qns

Your answer?
Actually you may refer back to your textbook, I mean for Q4.

2012-01-21 14:57:01 補充：
3(b)(ii) In NCl3, there are one lone pairs of electrons and three bond pairs of electrons (N-Cl) in the central atom N. Similarly, there are one lone pairs of electrons and three bond pairs of electrons (N-H) in the central atom N. Therefore, they both give a shape of trigonal pyramidal.

4(a) Add the sample to a beaker. Add distilled water to the beaker and transfer all washings to the 100 cm^3 volumetric flask. Then add up the solution to the graduation mark by adding more distilled water.

2012-01-21 22:13:23 補充：
I dunno, because you didn't give the mark of the respective questions.

2012-01-21 22:15:58 補充：
For 3b, you must state that there are 1 lone pair of electrons and 3 bond pairs of electrons (for criteria of forming trigonal pyramidal). Here you may lose 1 mark.

2012-01-21 22:17:50 補充：
For 4a, the last line "... up to the mark.". Specify what the mark means, i.e. it is graduation mark, such keywords should not be missed, or otherwise the marker may have poor impression on your answer.

2012-01-21 22:18:29 補充：
The above and the answer are just my opinions, anyway, just wait patiently for the marking scheme, it should be posted in hkeaa in early Feb.

3bii) since both H and Cl share 1 elctron with N .there are 1 lone pair in the outermost shell of N. the repulsion of lone pair and bond pair is greater than that of bond pair and bond pair . So, the shape of NCl3 and NH3 are both trigonal pyramidal

2012-01-21 12:04:23 補充：
4a.put the sample into the beaker and then add little distilled water into the beaker. add the solution into 100cm3 of volumetric flask. rinse the beaker with distilled water and then add the washings into the volumetric flask up to the mark.

2012-01-21 20:22:32 補充：
我原先答案是否也差不多能得分了?