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[Maz]

This one :/ ! @ do u know
XPFMember
View attachment 12749

Since the total mass is 160, how much does Sulphur contribute to it?
= 64 (Cu) + 32 ( S) + 16*4 (O2)
Therefore, sulphur contributes 32g of the total 160g.

 

[Spunkyfarhan]

Since the total mass is 160, how much does Sulphur contribute to it?
= 64 (Cu) + 32 ( S) + 16*4 (O2)
Therefore, sulphur contributes 32g of the total 160g.

Ohh thanx ! so this is da way !!!! Lolz!@@! JazakAllah@

 

[Tekno-M]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w11_qp_11.pdf
Q31. Can anyone explain why it's B.

 

[Maz]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w11_qp_11.pdf
Q31. Can anyone explain why it's B.

The main composition of dry air is nitrogen and oxygen.
Since,nitrogen is 78% in air.
78/100*x=120 ( as all of the oxygen is used up)
x=120*100/78
x=153
The nearest is 150.

 

[angel G]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s10_qp_11.pdf
Please explain me Q 22 and 26 !!

 

[JustineBerry]

A chemical engineer plans to produce hydrochloric acid.
Which metal is best for the reaction container?

A copper
B iron
C magnesium
D zinc

Could someone please explain why the answer is A? :s

 

[Rania MD]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s10_qp_11.pdf
Please explain me Q 22 and 26 !!

22-you must make hydarted crystals thus, you first need to filter off your solution and keep the residue which are the crystals. Then you will repeat the procedure of adding CuO to the acid as to concentrate the crystals. Then you will filter off again and will then wash the crystals. You cannot heat the crystals as the question clearly asks for Hydrated crystals. Heat will certainly remove the water giving anhydrous crystals. so teh correct order is 2-1-2-4

26- A and B are eliminated directly as both chlorine and fluorine are more reactive than bromine so they aren't displaced thus no colour change is observed
for C, Fluoride ions are more reactive than chloride ions thus again no dsiplacement takes place and the solution doesnt change colour
Yet, for D , the correct answer, Chlorine is more reactive than iodine thus it will displace the iodide ions from the solution and will result into sodiumchloride and iodine. I2 which is iodine solution is red-brown in colour and this is what causes a dark colour to be formed from colourless to dark brown.

 

[Rania MD]

A chemical engineer plans to produce hydrochloric acid.
Which metal is best for the reaction container?

A copper
B iron
C magnesium
D zinc

Could someone please explain why the answer is A? :s

the metal must be less reactive than Hydrogen or else the acid will react with the metal meaning that hydrogen will be displaced by this reactive metal. So you must choose a less reactive metal, less reactive than hydrogen. Only copper is less reactive than hydrogen thus copper will not react with the acid to try and displace these hydrogen ions.
The reactivity series for metals is
K
Na
Ca
Mg
Al
C
Zn
Fe
Sn
Pb
H
Cu
Ag
Au
Pt

 

[JustineBerry]

the metal must be less reactive than Hydrogen or else the acid will react with the metal meaning that hydrogen will be displaced by this reactive metal. So you must choose a less reactive metal, less reactive than hydrogen. Only copper is less reactive than hydrogen thus copper will not react with the acid to try and displace these hydrogen ions.
The reactivity series for metals is
K
Na
Ca
Mg
Al
C
Zn
Fe
Sn
Pb
H
Cu
Ag
Au
Pt

Oh my God I feel so stupid x_x
Thank you!

 

[Rania MD]

Oh my God I feel so stupid x_x
Thank you!

nah don't worry about it, and you're most welcome

 

[Lyfroker]

chemistry
w09 q#14
variant 2

 

[JustineBerry]

chemistry
w09 q#14

Variant?

 

[angel G]

22-you must make hydarted crystals thus, you first need to filter off your solution and keep the residue which are the crystals. Then you will repeat the procedure of adding CuO to the acid as to concentrate the crystals. Then you will filter off again and will then wash the crystals. You cannot heat the crystals as the question clearly asks for Hydrated crystals. Heat will certainly remove the water giving anhydrous crystals. so teh correct order is 2-1-2-4

26- A and B are eliminated directly as both chlorine and fluorine are more reactive than bromine so they aren't displaced thus no colour change is observed
for C, Fluoride ions are more reactive than chloride ions thus again no dsiplacement takes place and the solution doesnt change colour
Yet, for D , the correct answer, Chlorine is more reactive than iodine thus it will displace the iodide ions from the solution and will result into sodiumchloride and iodine. I2 which is iodine solution is red-brown in colour and this is what causes a dark colour to be formed from colourless to dark brown.

thank you !!

 

[GorgeousEyes]

no.26 , June2000.
no.20,June2002.
no.4,June2009.
no.4,June2010 .
Please some1 explain them .

 

[Lyfroker]

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

 

[Lyfroker]

Variant?

2

 

[JustineBerry]

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

Copper only reacts with nitric acid!

 

[JustineBerry]

no.26 , June2000.
no.20,June2002.
no.4,June2009.
no.4,June2010 .
Please some1 explain them .

For June 2010 question, The number of protons will be equal to the number of electrons. The diagram specifies that there are 9 particles in the nucleus. So if there are 4 protons in the nucleus, the remaining 5 particles will have to be neutrons.

 

[JustineBerry]

2

The answer should be C..

 

[zaid1q]

Plz help Q 31http://www.xtremepapers.com/papers/CIE/Cambridge%20IGCSE/Chemistry%20(0620)/0620_w11_qp_11.pdf