POST YOUR BIO AND CHEM PAPER 1 DOUBT HERE !!!!

[Jspake]

there are 2 different ways to solve it.

1) I don't know if you have this in ur text book or not, but there is an experiment like this in my text book, where they say that the sample of air is 100 and the volume decreases by 20 so that the syringe will read 80. This is because there is 20% of oxygen in air and this reacts with the copper, so what is left is 80 cm3 of air/ or because it is 100, you can just say 20% reacted and 80% is left. So with that example in mind, you can just do cross multipication and you get 150.

2)Another way you could do it is by using percentages in maths, knowing that there is 20% if oxygen in air.

Thanks a lot!

 

[Jspake]

the percentage of oxygen in the air is 20% and so 30 cm3 will be 20% of the sample of air (as in this reaction only oxygen is used up) and 20/100x=30 then x=150 cm3

Thanks a lot!

 

[balloonsandhighlighters]

i just explained it on the other sticky page but i will explain it again. well as u know sodium is more reactive than hydrogen and so it will produce hydrogen and not the metal but copper is less reactive than hydrogen and so copper will be produced and so we eliminate 3 and 4, now we have either 1 or 2, it is 2 because the metal is always deposited on the cathode which is 2

ok thanks a lot i get that, so nickel contains sodium right ? because the electrolyte has to be a salt solution of the metal that plates the objet?

 

[Abu mota]

ok thanks a lot i get that, so nickel contains sodium right ? because the electrolyte has to be a salt solution of the metal that plates the objet?

no bro, he is not plating using the electrodes, you can plate using the electrolytes, the electrode has to be the same as the salt so that we dont change the solution alot, but u can use the electrolyte only. if u dont understand ask again

 

[MariamHASAN]

CHEMISTRY PAPER 1 OCTOBER NOVEMBER 2006 QUESTION 27
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w06_qp_1.pdf

 

[Evangeline]

ameen u will get A*s too

thank you lovely sis
how are ur preparations so far

 

[Abu mota]

CHEMISTRY PAPER 1 OCTOBER NOVEMBER 2006 QUESTION 27
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w06_qp_1.pdf

MgO cant be reduced by carbon but CuO can be reduced by carbon and so the MgO will stay as it is but the copper oxide will be copper and carbon dioxide and carbon dioxide turns limewater cloudy and so the answer is B

 

[MariamHASAN]

MgO cant be reduced by carbon but CuO can be reduced by carbon and so the MgO will stay as it is but the copper oxide will be copper and carbon dioxide and carbon dioxide turns limewater cloudy and so the answer is B

thanks

 

[MariamHASAN]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w07_qp_1.pdf

qustion number 11 october november 2007 i donot get it

 

[phantom]

Just a quick question, Which is more important while preparing for Paper 1, solving as many past papers or revising the notes thoroughly??

 

[Abu mota]

Just a quick question, Which is more important while preparing for Paper 1, solving as many past papers or revising the notes thoroughly??

solving past papers in my opinion

 

[MariamHASAN]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w07_qp_1.pdf

question 20 also

 

[Abu mota]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w07_qp_1.pdf

qustion number 11 october november 2007 i donot get it

is the answer A? i did it with trial and error, i dont think there is another way, i did it like that x+ 8O2=CO2+H2O and then when i tried number 6 on CO2 but it never balanced but when i tried number 5 on CO2, it did balance. did u understand?

 

[phantom]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w07_qp_1.pdf

question 20 also

Carbon reacts with Oxygen forming CO2, which escapes as a gas, while CuO is a solid which settles, so Carbon's Mass decrease, and Copper's Mass Increase.

 

[Abu mota]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w07_qp_1.pdf

question 20 also

copper will increase but carbon will decrease because when copper is oxidised it will turn into copper oxide which increase its mass however when carbon is oxidised it turns into CO2 which escapes causing a decrease in mass and so the answer is B

 

[Abu mota]

is the answer A? i did it with trial and error, i dont think there is another way, i did it like that x+ 8O2=CO2+H2O and then when i tried number 6 on CO2 but it never balanced but when i tried number 5 on CO2, it did balance. did u understand?

srry i did a stupid mistake the answer is B i did it in the same way but i just made a silly mistake, i will explain it again just in case write the formula x+8O2=CO2+H2O and try to balance it with each one until one of them balances, so it is basically trial and error.

 

[MariamHASAN]

srry i did a stupid mistake the answer is B i did it in the same way but i just made a silly mistake, i will explain it again just in case write the formula x+8O2=CO2+H2O and try to balance it with each one until one of them balances, so it is basically trial and error.

thanks yes i got it

 

[areebaization]

thank you lovely sis
how are ur preparations so far

umm it's good am like just doing 3-4 papers per day.
Hows ur prep?

 

[balloonsandhighlighters]

no bro, he is not plating using the electrodes, you can plate using the electrolytes, the electrode has to be the same as the salt so that we dont change the solution alot, but u can use the electrolyte only. if u dont understand ask again

oh alright thank you i never knew that lol thanks a lot

 

[phantom]

can anyone help me with this question?

After sexual intercourse, sperm can survive for 3 days in the uterus and oviducts. Assume
ovulation can occur any time from day 13 to day 15.
If an egg cell lives up to 2 days after ovulation, how long is the fertile phase of the menstrual
cycle?
A 5 days B 6 days C 7 days D 8 days

Which year, session, and Question number??