Science Practical Olvl
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Do you smell the gas? Chlorine has a distinctive pungent smell. I seriously doubt any reaction will give Chlorine gas.Originally posted by abyone:I tested for carbonate... carbonate present... carbon dioxide gas present... effervescence shown
Then, I tested for Chlorine... ALSO Present?!?! White ppt formed
Lastly, Zinc present too...
Due to lack of time to think, I left my salt as Zinc Chloride
Haizz,,, i heard later on from my sci teacher, it was zinc carbonate...
So how many marks will I be deducted?!?! I left all present ... and salt as Zinc Chloride...
I suspect Chlorine was present in my test due to my improper cleaning of test tube ... T.T
S2pid Physics used up so much of my time...
I drew a best fitting line T.T coz 1 of my points went out of the curve shape...
Reactions that give chlorine gas usually involve concentration HCl any concentrated reagents OR Organic reagents.
Adding dilute nitric acid to a sample will not give any Chlorine gas.
So the sample is definitely carbonate.
Just remember, to get chlorine gas is never easy. If chlorine gas is produced in like effervescent state, you have to do it in fume board.
19,000mg·min/m3 is lethal dose to 50 percent of exposed adults. If everyone gets chlorine effervescent, all the students inside the lab might have died.
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The normal grades without moderation is this(shown below):Originally posted by felirox:why issit like that?
As you can see, in order to achieve A1 without moderation, it'll require 75% marks. If for a particular year, the many students did very well for the paper, then quite a lot of students scoring A1 and this could be due to many reasons. One of it could be the paper is too easy, so moderation is a way to filter and accurately grade the better students with the weaker ones.
This is what the happened after moderation. A crude but realistic example: In order to obtain A1, you need to score at 84% of the marks.
As you can see from the graph because the A1 bench is push up, there will be lesser students scoring A1. This will preserve the integrity and the quality of students from that particular batch.
Similarly.. If the paper is too hard and very few people scored A1, the authorities may lower the boundaries so that a reasonable amount of student still can get A1.
Clear?
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In school, we are too used to the A1 -75% etc bench mark. It is in fact a killer mentality to think this way.
In an actual national exam, chances of getting A1 with 75% is too low or not possible. You might need at least an 85% to get A1 after moderation! -
That's cruel...Originally posted by Darkness_hacker99:In school, we are too used to the A1 -75% etc bench mark. It is in fact a killer mentality to think this way.
In an actual national exam, chances of getting A1 with 75% is too low or not possible. You might need at least an 85% to get A1 after moderation!
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I am a victim of A1-75% mentality victim.Originally posted by felirox:That's cruel...
Don't be like me ok? Buck up
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yea lo..Originally posted by felirox:That's cruel...
does it also mean 50/100 may not be equal to a C6? -
Yes.Originally posted by hatemeifuwantto:yea lo..
does it also mean 50/100 may not be equal to a C6?
With a bit of luck, it can be C5 -
so now it all depends on the o lvl papers eh? see how tough or easy the paper is...darn.
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Jia You!Originally posted by felirox:so now it all depends on the o lvl papers eh? see how tough or easy the paper is...darn.