Chemistry Revision Thread

rightiho
polyethene: cling film and packaging. waste bags and containers. some water pipes made from the thicker version of it.
Polypropene: Effective barrier agaisnt water so used in housewares and for fibre for carpetting and ropes and stuff
Polysytrene: i dont know specifically but packaging utilitiess as well as insulation?
PVC- plastic pipes, vinyl coatings, wire insulation and like...wats it called acylic resins? as a binder for laminated glass.

problems are most are non-biodegradable and some cannot be reecycled due to thermosetting nature. so yeh...u cant burn em because they release toxic gases and burial sites are bad 4 environment.

btw....does anyone know why ammonia is NH3 but the ion is NH4 + ? i cant remember.

Reply 102

It would be great if someone explains the answer to question 19a ii on the 2003 AQA 3421 H paper?

I know the answer but dont have a clue about it...I always though concentration is measured in dm^3 per mole.

Would help everyone here i'm sure: http://www.aqa.org.uk/qual/gcse/qp-ms/AQA-3421H-W-QP-Jun03.pdf

Reply 103

Erm, instead of moles its grams it looks like. Instead of finding the moles from the grams, you'd find the grams from the moles (previous q 19 ai)

Reply 104

In an experiment, it was found that the ethanoic acid present in a 15.00cm3 sample of vinegar
was neutralised by 45.00cm3 of sodium hydroxide solution, of concentration 0.20 moles per
cubic decimetre (moles per litre).
The equation which represents this reaction is
CH3COOH + NaOH CH3COONa + H2O
Calculate the concentration of the ethanoic acid in this vinegar:
(i) in moles per cubic decimetre (moles per litre);

Repeat post

(45*0.2)/1000 = 0.009

0.009=(15*Concentration)/1000

9=(15 x concentration) (times each side by 1000)

9/15 = concentration(divide each side by 15)

0.6 = concentration

Reply 107

Excalibur

Do we need to know that for Double Award? *alarmed*

Reply 108

we dont so this in our syllabus....whats the 1000 for again?

Reply 109

^NO! not for aqa anyway

Q: Describe the strucure and bonding in a metal

Reply 110

Krystal

we dont so this in our syllabus....whats the 1000 for again?

Divide by 1000 because its in cm^3, the unit is dm^3(litre^3)...If the question said 25 litres then you dont divide by 1000

Reply 111

Its titration calculations. thats what i was talking about earlier - moles of a solute. (divide by 1000), must only be for OCR :s

Reply 112

^Cheers for your post btw finally figured out why :smile:

Reply 113

alpesh24

Could someone please list all the formulas needed for AQA triple science please?

many thanx in advance

Reply 114

davidjones90

Divide by 1000 because its in cm^3, the unit is dm^3(litre^3)...If the question said 25 litres then you dont divide by 1000

OH ryt...is that it! ...i can be so slow sometimes. :p:

and i get the moles of a solute thing now...hehe...thanx.

Reply 115

jonnymeldrum

err, yes you do need moles and titration for aqa seperate science. it is from aqueous and organic chemistry.

Reply 116

How many of you are really nervous about this test 2moz? I'm really crap at most chemistry stuff, but fluked an A* in my mock O: xD Still i spose it's only my own fault, im watching the brazil match and im on here :wink:

Reply 117