Combined Chemistry Qns

ceecookie SG

Can anyone explain the respective answers for this question?None of my notes explain the answers.

3b) Why is the correct answer E? AFAIK proton number is the same as the electrons' so it should be B since it got 5 electrons. Confused

eagle SG

heh me return chemistry to teacher liao

^tamago^ SG

A = Beryllium
B = Nitrogen
C = Flourine
D = Oxygen
E = Boron

A is metal. The rest are non-metals.

(b) E. A lone Boron atom indeed has 5 protons and 5 electrons.
(c) D. O2
(d) A and C. A as reducing agent, C as oxidising agent.

ceecookie SG

Originally posted by ^tamago^:

(b) E. A lone Boron atom indeed has 5 protons and 5 electrons.

But the Boron as shown is not lone isit?Why does it show only 3 electrons?

^tamago^ SG

outer shell, outer shell.........

ceecookie SG

Oh i get it.
As in total,not in the outer shell alone.

2.3 = 5

2.5 = 8.

^tamago^ SG

yeah lor. Embarassed

B = 1s²2s²2p¹ = 2+3.

HyuugaNeji SG

fe2+ solution is green lo...most solution with fe2+ will be green...what to do...god dictate it to be green. light spectromecy due to energy levels of electrons cause something to be of a different color.

What a chemistry student can do is guess lor. So can guess from 1 out of 100+ elements right? There are only 100+ elements in this world. Master all the elements and how they combine with one another and you will be god.

Darkness_hacker99 SG

Atomic orbital is not under O level syllabus.

Darkness_hacker99 SG

To know what's metal R, you must know the answer for green ppt U.

Metal R + Sulphuric acid = R sulphate + Hydrogen

R sulphate + Sodium Hydroxide = R hydroxide + Sodium Sulphate

If green ppt is obtain, it's Iron(II) hydroxide.
If red/brown ppt is obtain, it's Iron(III) hydroxide.

From this Sodium hydroxide test, we can tell the the Cation ion is Fe2+
Therefore the Metal R is Iron.

First you must know that the use of acidified Barium chloride is to test for presence of the of sulphate ions. If sulphate ions is present, then white ppt will be obtain.

Background information that you might need to know.

Chlorine is an oxidizing agent. Which mean, it'll cause something to oxidized. So in this case, Fe2+ is oxidized to Fe3+

The brown solution after bubbling is Iron(III) sulphate.

HyuugaNeji SG

Here's a question for chemists:

1) Why is oxygen gas colourless? Very Happy (Dont tell me because you cant see it)

Here's a question for biologists:

1) Why is glucose sweet? (Dont tell me it contains sugar or crap cos why is that crap sweet?)

^tamago^ SG

extra info. Sad

Darkness_hacker99 SG

Very Happy

^tamago^ SG

Embarassed

Darkness_hacker99 SG

Why is glucose sweet?

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Taste.html#sweet

I hope this page can help you.

HyuugaNeji SG

thanks. that's a good site.

A chem prof told me that they are still working on why some stuff like sucrose, glucose and fruitose are sweet. They guess it has to do with the structure of the chemicals and their bondings.

And this brings me to the next question: Why is Sodium saccharin so much sweeter than the rest?

Pls refer to: http://en.wikipedia.org/wiki/Sweet who dare to drink sodium saccharin product?

Darkness_hacker99 SG

Yar. Structures and bonding does plays a huge part. But we must not overlook the Biological part of the research. Because to understand and solve the mysteries of this complicated and complex problems, it definitely will require people from different specialization.

Does your prof's team have biologist and neurologist?

HyuugaNeji SG

No. I am not a chemistry nor biology nor life science student. I just ask this question to the chem prof (GEM module) for fun. Cos i pay school fees mah. Very Happy