Biology; Chemistry; Physics: Post your doubts here!

[robinhoodmustafa]

Q.1 (C,D,E) Can anyone please explain me the calculations clearly? Have a exam tomorrow.

Wait! I will get back to you on that..

 

[sourov97]

So that no pressure builds up inside and prevent the apparatus from exploding.

Just remember the Pressure cooker.. Pressue builds up.If there is no Exit for the pressure(Heat) than It can explode

may be u are wrong....the lid is placed to prevent the powdered MgO from escaping...as written in 5070_s09_ms_4

 

[Suchal Riaz]

U be doing Merchant Paper... Am I right
I just did that q

Sodium : White lilac flame, Very Vigorous reaction, metal be floating on top (Because grp 1 metal r light) and Metal oxide be seen below

Iron: It doesnot react with water so No Reaction

I am Confuse that it Iron is presence of water can get rusted so why not Iron Can react with Water?

it rusts in presence of oxygen ang takes many days to react

 

[AhsanAfzal]

may be u are wrong....the lid is placed to prevent the powdered MgO from escaping...as written in 5070_s09_ms_4

yah he is right i just saw that paper too and it says "to prevent product from escaping"

 

[simranlalchand]

U be doing Merchant Paper... Am I right
I just did that q

Sodium : White lilac flame, Very Vigorous reaction, metal be floating on top (Because grp 1 metal r light) and Metal oxide be seen below

Iron: It doesnot react with water so No Reaction

I am Confuse that it Iron is presence of water can get rusted so why not Iron Can react with Water?

yes you are right i am doing merchant paper

 

[robinhoodmustafa]

may be u are wrong....the lid is placed to prevent the powdered MgO from escaping...as written in 5070_s09_ms_4

This can also be an another reason.

How can powder mgo be prevented from escaping. You open the lid. The Powder flows out

 

[robinhoodmustafa]

Ishrar Afrida

Sorry I dont take Practical paper

 

[Suchal Riaz]

robinhoodmustafa can u tell us the paper if u think u are not cheating on ur teacher. i m not convincing u to do it. no offences.

 

[sourov97]

This can also be an another reason.

How can powder mgo be prevented from escaping. You open the lid. The Powder flows out

Firstly, lids are lifted to prevent pressure build ups, not placed...this would rather result in pressure build up.
Secondly, powdered MgO is very light and can blown by the heated air that are moving in the crucible with relatively fast speed.

 

[robinhoodmustafa]

robinhoodmustafa can u tell us the paper if u think u are not cheating on ur teacher. i m not convincing u to do it. no offences.

Which paper? U mean Important Topic by Merchant

 

[Suchal Riaz]

Which paper? U mean Important Topic by Merchant

the one everybody is discussing.
i feel like peoples are whispering into each other's ear and i m just watching them curiously without knowing what they are saying

 

[Khadija_1234]

http://papers.xtremepapers.com/CIE/...l O Level/Chemistry (5070)/5070_w12_qp_41.pdf

Please explain whats happeing in Q8 :/

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w12_qp_41.pdf

Please explain whats happeing in Q8 :/

the level rises or goes down due to change in rate of displacement as N2 and CO have same Mr their rate is same so no displacement of water level.

 

[robinhoodmustafa]

the one everybody is discussing.
i feel like peoples are whispering into each other's ear and i m just watching them curiously without knowing what they are saying

That was Imran Merchant Guess paper but I am not sure whether it real or no. The Paper has good questions. really helpful for practise

check the thread
https://www.xtremepapers.com/commun...t-bio-chem-phy-and-economics-post-here.24552/

switch through pages.. U will see a person has uploaded a doc.

 

[Dawarkazi]

answer please!
question 2

 

[sourov97]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w12_qp_41.pdf

Please explain whats happeing in Q8 :/

the water level didn't change...this means that if there was any change of gases between the porous pot and the inverted beaker, the molecular mass of that gas should be equal to that of CO (12 + 16 = 28).
(d) nitrogen (gas) is the answer. (14 + 14 = 28)

 

[Suchal Riaz]

answer please!
question 2

iron react with water in presence of oxygen very slowly, it takes weeks to observe a change. it reacts just enough fast with steam to notice.
therefore:
1-sodium react very violently, it floats on the surface of water(low density), turns red hot(due to exothermic reaction), produces a gas(hydrogen) which burns(although it only burns after potassium and higher but ms accept it)
2- no reaction.

 

[fatima0000]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_w08_qp_4.pdf
Q 7
explaination?

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w08_qp_4.pdf
Q 7
explaination?

the change is due to difference on rate of diffusion. so the gas must have same molecular mass as N2. 28 is Mr of N2 so is of CO. therefore CO is answer. same Mr same diffusion rate, no change.

 

[AhsanAfzal]

which gases move through porous pot? Suchal Riaz Saad Mughal