chem p1 doubts

[NabzJ]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w09_qp_11.pdf
Please explain Q 4 and Q 23 !!

4= A, cuz if 8 more electrons are present then it must be in the same group , and it could be a noble gas , or anything else , who knows?>..
so both are correct.

 

[aliiiiiiiiii]

1

i hope am not late
i think its B
because u will have to find the % of oxygen. which is in 100% O2 is like 27-28% fined the % when its 120 it will be almost 30-31 then add 120 u will get 150 or 151 which is B
hope i helped
sorry O2 is 21% it will come close

 

[angel G]

4= A, cuz if 8 more electrons are present then it must be in the same group , and it could be a noble gas , or anything else , who knows?>..
so both are correct.

Thank you !

 

[aliiiiiiiiii]

r u sure that all salts have pH 7

Yes all salts have pH 7

no not all salts havee ph 7
only the salts made from acids and bases that are in the same level like strong acid+strong base =ph7 salt
stron acid +week base =acidic salt

 

[sammm]

i hope am not late
i think its B
because u will have to find the % of oxygen. which is in 100% O2 is like 27-28% fined the % when its 120 it will be almost 30-31 then add 120 u will get 150 or 151 which is B
hope i helped

but how can we predict %of a gas

 

[Beedo]

Please can someone tell me reaction conditions for famous reactions like Haber,contact,cracking ... etc

 

[thats_me]

n in o/n 11 .How can we easil
y predict the ans of ques31 as B .plz tell me a method to do this.

Ohkaye..
The percentage of oxygen in air is 20-21%
so lets take the percentage of air as 100% & when air is used up as 80%
As in the question they gave the volume after oxygen is used is 120
We need to cross multiply :
If 100 gives 80, then how much gives 120?
(100*120)/80 =150

 

[sammm]

Ohkaye..
The percentage of oxygen in air is 20-21%
so lets take the percentage of air as 100% & when air is used up as 80%
As in the question they gave the volume after oxygen is used is 120
We need to cross multiply :
If 100 gives 80, then how much gives 120?
(100*120)/80 =150

oh thanks so sweet of u

 

[Beedo]

Also need help pleaaaase in uses of metals and alloys .. I never answer them correctly
need a pdf about them or something like that please urgently

 

[thats_me]

Please can someone tell me reaction conditions for famous reactions like Haber,contact,cracking ... etc

Haber..
Temp :450 degrees
prssure : 200 atm
Catalyst :iron
Contact...
Temp :450 degrees
prssure : 2 atm
catalyst : vanadium (V)oxide
Cracking : Vapour of a liguid Alkane is passed over a heated catalyst to make ethene (so high temp & catalyst)

 

[thats_me]

oh thanks so sweet of u

Ur welcum

 

[Beedo]

Haber..
Temp :450 degrees
prssure : 200 atm
Catalyst :iron
Contact...
Temp :450 degrees
prssure : 2 atm
catalyst : vanadium (V)oxide
Cracking : Vapour of a liguid Alkane is passed over a heated catalyst to make ethene (so high temp & catalyst)

Thanks

 

[thats_me]

Thanks

Ur most welcum

 

[Beedo]

No 38 in Nov11 V12
Why is it D?

 

[thats_me]

No 38 in Nov11 V12
Why is it D?

It's not A it's D It's the one with the highest % of diesel