Chemistry SPA

last SG · 2008-11-05T20:41:46+00:00

Are you Secondary 3? And your teacher should have told you what's coming out. What have you been practising in the labs all these time?

Darkiish SG

what is experimental errors and precautions?

kenn3th SG

Manage your time well, dont worry about washing up, you will be given time at the end of the SPA, (outside doing time).

Rinse apparatus with tap water then distilled, if you are the 2nd batch.

the teacher (your school) will tell you that it's a new batch and you do not need to wash.

kenn3th SG

what is experimental errors and precautions?

You cannot write errors that you can prevent.

Write errors like:

acidic carbondioxide reacts with the alkali, thus reducing the concentration of alkali and hence resulting in lesser volume of 1mol/dm3 (eg) of hcl (or anyother acid) reacting with the alkali.

kenn3th SG

precautions - if you are using a burnson burner (unlikely) precaution is, close air hole, wear goggles then light. This is to prevent flash back of flames.

Darkiish SG

if its the experiment on tiltrations, what is the possible answers for precaution and error made.

kenn3th SG

It will not be straight forward - read carefully.

for eg: container A contains 2mol/dm3 of H2So4.

when they say, 50cm3 from container A, make sure it's A, double check, if not, later it's 50cm3 from container B.

(essential) in calculations for titration. All info up there.

Remember to label properly. Furthermore, after you label your answers, remember UNITS.

if not for eg, you write 5.00

5.00 what?

5.00 monkeys or cm3?

kenn3th SG

if its the experiment on tiltrations, what is the possible answers for precaution and error made.

the acidic co2 from the air react with alkali. (previous page). error.

Precaution - read at eye level to prevent inaccurate volumes of chemicals measured.

do note: Use scientific terms.

kenn3th SG

I have told you what i know.

I may leave out somethings.

One last thing would be - Handphones, electronic devices, PDAs, pages, all in your bag. Outside the room. Pls switch off and put to silent.

and no communication. you will be sitted accordingly to your index. check the arrangement.

next, would be, if your lab is small, you guys will be next to each other - do not communicate still. Or look at other's script.

Note: Learn calculations - Moles.

Pg 298 (chapter 18 is important). read up.

All the best.

Darkiish SG

my school have not yet covered the topic on mole. so the question given will not be given in moles? units is a must and calculations must will rounded off to their precisions.

kenn3th SG

have not covered =/

Then your Spa should not have titration. Titration and calculations are inter connected. So highest bet would be QA. test for cations and anions.

I said, should not, but not meaning, will not.

Post back tml on the topic.- but remember, not the answers.

Darkiish SG

ok thx

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