Biology; Chemistry; Physics: Post your doubts here!

[snowbrood]

 

[snowbrood]

can anyone solve these please these are the answers
5a i reactants: (aq) (s);
products: (aq) (l) (g)
1
ii 25/1000 x 1.5 x 24 = 0.9 dm

b 0.75 mol/dm3
;
25 cm

 

[scouserlfc]

That convinces me that the percentile doesn't apply to O levels.

ILL give u a proof,ask any experienced teacher and they will always tell you that without percentile CIEs marking wont exist its like their back bone and most of us would get b or c ! Also the distinction in reality is not necessarily attained by a guy who got full marks but he gets the highest marks so he is given the distinction also another thing is find that notice given by CIE when they introduced A* grade for O Levels in one of the FAQs there it is indirectly told abt PERCENTILE !
Now are u good !

 

[scouserlfc]

can anyone solve these please these are the answers
5a i reactants: (aq) (s);
products: (aq) (l) (g)
1
ii 25/1000 x 1.5 x 24 = 0.9 dm

b 0.75 mol/dm3
;
25 cm

problem is we require to read the whole ques to answer this !

 

[snowbrood]

problem is we require to read the whole ques to answer this !

i have posted the entire question

 

[Fallen316]

ILL give u a proof,ask any experienced teacher and they will always tell you that without percentile CIEs marking wont exist its like their back bone and most of us would get b or c ! Also the distinction in reality is not necessarily attained by a guy who got full marks but he gets the highest marks so he is given the distinction also another thing is find that notice given by CIE when they introduced A* grade for O Levels in one of the FAQs there it is indirectly told abt PERCENTILE !
Now are u good !

 

[malay]

i have posted the entire question

give the answer than ill tell mine

 

[scouserlfc]

i have posted the entire question

Yaar im not able to see it so give the link please or just tell the year ill find it myself

 

[Rimsa]

View attachment 10811

i) HCL is always aq. CACO3 is always solid. water liquid and CO2 gas...
ii) calculate moles of HCl. using formula, moles= molarity *vol/1000
the solve it by ratio method between HCl and CO2. then convert moles into volume

 

[malay]

View attachment 10811

2- 12.5cm3??

 

[daredevil]

Chemistry question:
Q. Which type of reaction occurs when soap is formed from fats?
A. hydrolysis
B.polymerisation
C.fermentation
D.substitution

plz explain too b/c i don't get the answer's logic

 

[snowbrood]

Yaar im not able to see it so give the link please or just tell the year ill find it myself

http://www.xtremepapers.com/papers/...al O Level/Chemistry (5070)/5070_w05_qp_2.pdf here it is Q5 a(ii),b

 

[malay]

Chemistry question:
Q. Which type of reaction occurs when soap is formed from fats?
A. hydrolysis
B.polymerisation
C.fermentation
D.substitution

plz explain too b/c i don't get the answer's logic

A?

 

[Rimsa]

Chemistry question:
Q. Which type of reaction occurs when soap is formed from fats?
A. hydrolysis
B.polymerisation
C.fermentation
D.substitution

plz explain too b/c i don't get the answer's logic

hydrolysis. its formed from glycerol that is a product of fat hydrolysis

 

[daredevil]

A?

yup

 

[daredevil]

hydrolysis. its formed from glycerol that is a product of fat hydrolysis

thnks but can u give some detail on fat hydrolysis? bcuz i don't think i did it and there is something about heating fat with aqueous NaOH .... but y are we using an acid in hydrolysis?? can u give some info about this and also realte it to fats. tanks in advance

 

[scouserlfc]

can anyone solve these please these are the answers
5a i reactants: (aq) (s);
products: (aq) (l) (g)
1
ii 25/1000 x 1.5 x 24 = 0.9 dm

b 0.75 mol/dm3
;
25 cm

the thing is that in 2 the gas produced is half the previous volume in experiment 1 so it has half the concentration of the solution used in 1 !
Play with the molarity equation and u will understand it and btw make volume a constant when u play !

 

[Rimsa]

thnks but can u give some detail on fat hydrolysis? bcuz i don't think i did it and there is something about heating fat with aqueous NaOH .... but y are we using an acid in hydrolysis?? can u give some info about this and also realte it to fats. tanks in advance

http://dl.clackamas.cc.or.us/ch106-06/images/66rxn05.JPG
The three ester bonds in the triester(fat molecule) are hydrolyzed to form glycerol and three fatty acids. These R groups are not necessarily the same, therefore the fatty acids are not necessarily the same.NaOH is used as a catalyst.

 

[Dukeofwin]

I can manage Chemistry, anyone here who is appearing for Add Maths! I'm like 2+2=6 in add maths!
Simply worse!
Any tips, or anything would work!

 

[scouserlfc]

I can manage Chemistry, anyone here who is appearing for Add Maths! I'm like 2+2=6 is add maths!
Simply worse!
Any tips, or anything would work!

Probably check out cambridgestudents.com and go to the subject page and find add maths u can get tips there !