physics and chemistry doubts!!

[Faiza Anwar]

how was urs?

it was good ! paper 1 was really nice.. which variant did u give?

 

[dubi2pro]

3 N-H bonds which are twice as mentioned in eq.
2x3=6
6x388= +2328
H-H is breaking so endo, nd N-H is forming so exo..
energy taken in for bond breaking is (944+1308=2252), while energy released in bond making is 2328..
energy released in bond making is more than energy taken in for bond breaking so forward reaction is exo..

thaaanks alot! really helped

 

[Faiza Anwar]

thaaanks alot! really helped

you are welcome !!

 

[Faiza Anwar]

@dupi2bro how do u take a snapshot of your screen? i try that on my laptop but it doesn't work..

 

[dubi2pro]

@dupi2bro how do u take a snapshot of your screen? i try that on my laptop but it doesn't work..

that prntscreen right on top corner of the keyboard, press it , go to paint, and press cntl+v to paste it! and then simply save to desktop!

 

[dubi2pro]

that prntscreen right on top corner of the keyboard, press it , go to paint, and press cntl+v to paste it! and then simply save to desktop!

dubi2bro? LOOL its Pro!

 

[Faiza Anwar]

that prntscreen right on top corner of the keyboard, press it , go to paint, and press cntl+v to paste it! and then simply save to desktop!

i used to press the prt sc many times but nthng happened now i know why.. thnks

 

[Faiza Anwar]

dubi2bro? LOOL its Pro!

yeah !! pro

 

[dubi2pro]

i used to press the prt sc many times but nthng happened now i know why.. thnks

 

[shadil.me]

it was good ! paper 1 was really nice.. which variant did u give?

1

 

[Faiza Anwar]

1

me too !

 

[shadil.me]

me too !

 

[Masha karroum]

 

[Masha karroum]

can someone explain please all these screenshot questions please

 

[Faiza Anwar]

View attachment 43233View attachment 43233

moles of oxygen=0.08dm/24=3.33x10-3
2 moles of oxygen react with one mole of methane so cross multiplication
(3.33x10-3 x 1)/2 = 1.67x10-3 mol of methane
now find volume of methane from volume=mole x 24
v= 1.67x10-3 x 24 = 0.040 dm
convert dm in cm
0.040x1000= 40 cm
now find percentage in 60 cm sample...
40/60 x 100 = 66.67 %
(note with all cm nd dm they are cubic)
hope u get it nd plzz ask if any doubt..

 

[Faiza Anwar]

can someone explain please all these screenshot questions please

there is only one Question !

 

[Masha karroum]

t

there is only one Question !

thankyou you so much helped loads

 

[Faiza Anwar]

t

thankyou you so much helped loads

your welcome... remember me in your prayers !! nd BEST OF LUCK !

 

[Faiza Anwar]

does any one have the notes for moles nd chemical formulae...?

 

[Hello090078601]

How to solve:

20 cm^3 of a hydrocarbon was burnt in 175 cm^3 of oxygen. After cooling, the volume of the remaining gases was 125 cm^3. The addition of aqueous sodium hydroxide removed carbon dioxide leaving 25 cm^3 of unreacted oxygen.


iii) Deduce the formula of the hydrocarbon and the balanced equation for the reaction.

Why does it say in the mark scheme that any combustion equation of an ALKENE would do? Why not an alkane?

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s13_qp_33.pdf