Physics, Chemistry and Biology: Post your doubts here!

[sma786]

The grade boundries are getting lower every year so I'm guessing it would be an A this year
If you're aiming for an A* in the end you have to get a max of 3 faults in paper 1, 10 in paper 3 and 5 in paper 6 ( my teacher told me this)

oo, thanks for the info =]

 

[JustAnotherPerson22]

is 60+ out of 80 bad in chemistry paper 3 ?

If you get 60/80 in p3, and lost like 10more in p1 + p6 combined then you're probably getting an A*(personal experience since this happened to me in chemistry last year)

 

[sma786]

which ppr was that?

all of them

 

[sma786]

If you get 60/80 in p3, and lost like 10more in p1 + p6 combined then you're probably getting an A*(personal experience since this happened to me in chemistry last year)

okay thats good, i can easily get an A then,, pray for me

 

[thats_me]

okay thats good, i can easily get an A then,, pray for me

Don't worry u sure will!

 

[JustAnotherPerson22]

okay thats good, i can easily get an A then,, pray for me

Haha I will for sure
Last year in my class we were 8 people and 6 managed an A* in chemistry and other two got A and B
so don't worry about numbers and do your best for now

 

[sma786]

Haha I will for sure
Last year in my class we were 8 people and 6 managed an A* in chemistry and other two got A and B
so don't worry about numbers and do your best for now

thanks for raising my hope or watever they say

 

[Penalopi]

Question: Is Naphta used as a fuel or just for house-heating systems? Which fraction exactly is it collected at? The book says nothing about it!

 

[Penalopi]

Naphtha*

 

[sma786]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w08_qp_03.pdf
Variant 1, question 4 (b ii) .. how do we find out the ratio ?

 

[thats_me]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w08_qp_03.pdf
Variant 1, question 4 (b ii) .. how do we find out the ratio ?

It's done by using the atomis mass.. Carbon 's atomic mass is 12 and Hydrogen's is 1..
(CH)n=78
= (12+1)n=78
=13n=78
n=78/13=6
so C6H6, the ratio will be 6 : 6 i.e 1 : 1

 

[Dashexdan]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w08_qp_03.pdf
Variant 1, question 4 (b ii) .. how do we find out the ratio ?

u first find the 92.3% of 78 that is for carbon=92.3/100*78=71.99 ,, round it of to 72,,,so carbons total molecular mass is 72 and the moles are 72/12(carbons molecular mass) so 72/12=6
72 is the total molecular mass of carbon in benzene thus 78-72=6 to find hydrogens tootal molecular mass in benzene and divide 6/1=6
thus the ratio is 6:6 by simlifying further 1:1

 

[sma786]

u first find the 92.3% of 78 that is for carbon=92.3/100*78=71.99 ,, round it of to 72,,,so carbons total molecular mass is 72 and the moles are 72/12(carbons molecular mass) so 72/12=6
72 is the total molecular mass of carbon in benzene thus 78-72=6 to find hydrogens tootal molecular mass in benzene and divide 6/1=6
thus the ratio is 6:6 by simlifying further 1:1

ooh lol, thanks. that was easy

 

[sma786]

A very dumb question i suppose butt ...
are hydrochloric acid and hydrogen chloride same ??

 

[thats_me]

A very dumb question i suppose butt ...
are hydrochloric acid and hydrogen chloride same ??

hydrochloric acid is aqueous where as hydrogen chloride is a gas ..

 

[sma786]

Write the ionic equation for the reaction between tin atoms and silver(I) ions ??

 

[thats_me]

Write the ionic equation for the reaction between tin atoms and silver(I) ions ??

Sn + 2Ag2+ ----> Sn2+ + 2Ag

 

[sma786]

Sn + 2Ag2+ ----> Sn2+ + 2Ag

yeah but y 2Ag?

 

[Manobilly]

There was 2Ag before ,we have to balance it.

 

[thats_me]

yeah but y 2Ag?

As it's in this way :
Sn - 2e- ---> Sn2+
2Ag2+ +2e- ---> 2Ag (then we add both the reactions)
=Sn + 2Ag2+ --->Sn2+ +2Ag (-2e- & +2e- get cacelled)