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[Lyfroker]

The answer should be C..

i knw dat but why?

 

[Lyfroker]

@сᴏᴏʟ сяуѕтᴀʟѕ

chemistry
w09 q#14
variant 2

why doesnt copper form copper(II) sulphate with warm dilute sulphuric acid?

 

[сᴏᴏʟ сяуѕтᴀʟѕ]

@сᴏᴏʟ сяуѕтᴀʟѕ

Assalam-o-alaikum wr wb..
Well...it is the electrolysis of concentrated aquesous sodium chloride..which means that chlorine will be discharged at the anode and hydrogen at the cathode...

the color of universal indicator will change to colorless as we know that chlorine bleaches it...
on the other hand i think that the color on the cathode is for the solution remaining...the solution remaining is sodium hydroxide which is alkaline so the color will be bluish purple...(such question we had in some other year also where they said that the products at cathode is sodiumn hydroxide)

if you didn't get it..feel free to ask

2nd question...bcoz it is lower in the series than hydrogen so it can't displace it...

 

[сᴏᴏʟ сяуѕтᴀʟѕ]

@сᴏᴏʟ сяуѕтᴀʟѕ

Assalam-o-alaikum wr wb..
Well...it is the electrolysis of concentrated aquesous sodium chloride..which means that chlorine will be discharged at the anode and hydrogen at the cathode...

the color of universal indicator will change to colorless as we know that chlorine bleaches it...
on the other hand i think that the color on the cathode is for the solution remaining...the solution remaining is sodium hydroxide which is alkaline so the color will be bluish purple...(such question we had in some other year also where they said that the products at cathode is sodiumn hydroxide)

if you didn't get it..feel free to ask

2nd question...bcoz it is lower in the series than hydrogen so it can't displace it...

more detail:

firstly hydrogen gas has no effect on the universal indicator paper...secondly the gas escapes so what is remaining at the cathode? sodium hydroxide..so the color will be blue!

 

[Lyfroker]

more detail:

firstly hydrogen gas has no effect on the universal indicator paper...secondly the gas escapes so what is remaining at the cathode? sodium hydroxide..so the color will be blue!

tnx a lot

 

[сᴏᴏʟ сяуѕтᴀʟѕ]

tnx a lot

Your welcome

 

[Lujain M.]

hey guys I dont understand why the ans to Q39 nov/2011 variant 1 is D :S

 

[FATIMAH]

how did you all solve this question ? i got the right answer but just want to confirm it ??

 

[princessanum]

hey guys I dont understand why the ans to Q39 nov/2011 variant 1 is D :S

could u just post the link...

 

[angel G]

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

 

[FATIMAH]

hey guys I dont understand why the ans to Q39 nov/2011 variant 1 is D :S

b/c t has the largest quantity of gasoline which is petrol which is used by cars (motor vehicles) even it has largest quantity of diesel u used by trucks which are also motor vehicles

 

[angel G]

how did you all solve this question ? i got the right answer but just want to confirm it ??


View attachment 12886

I THINK it will be like hmmm.....................................
see oxygen present in the atmoshere is 21% . If at the end of the reaction it is 120 cm3 , then the starting cannot be C and D ! So the left are 132 cm3 and 150 cm3 . 132 cant be the answer because it less than 21 % . So the left is 150 cm3 (which is the ans ).

 

[Lujain M.]

b/c t has the largest quantity of gasoline which is petrol which is used by cars (motor vehicles) even it has largest quantity of diesel u used by trucks which are also motor vehicles

So I choose the one with the most gasoline ?

 

[Lujain M.]

how did you all solve this question ? i got the right answer but just want to confirm it ??


View attachment 12886

hey I solved it like
I assumed the starting was "x"
so "x"-(21%ofx)=120
so --> x- 0.21x = 120
so we get 0.79x=120
therefore, x=120/0.79 which is equal to 151 cm3 approx.
I hope you got the way I used

 

[JOEJOE]

chemistry
w09 q#14
variant 2

ok listn the arrangement of the apparatus allows OH- ions to move to the cathode but prevents sodium to leave the cathode so at the cathode rxn occurs Na+ + OH- --> NaoH colour turns blue due to ^pH

 

[JOEJOE]

fatima do ratio and proportion

21(%of O2) : 120
100(%of all gases including o2) : x

Cross multiplication

 

[Ahmed Raouf]

i have two questions i wish someone would explain to me.
Its from the o levels chemistry may june 2003 questions 5 and 32.
I read the er but don't understand anything form it.

 

[JustineBerry]

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

Atom X has 8 more electrons than atom Y, so they could be in Group 8, like Helium and Neon, etc. Thus, both students could be right and the answer is A

For Q23, Copper as a metal does not react with any acid except for nitric acid. So option 1 is completely eliminated. The remaining options are 2 and 3, which is C

 

[FATIMAH]

fatima do ratio and proportion

21(%of O2) : 120
100(%of all gases including o2) : x

Cross multiplication

can u plz explain it further

 

[FATIMAH]