Chemistry Paper 2

[ibadsiddiqi]

@tomorrow is your last exam??!! I have accounts p2 and both add maths left

 

[no.mercy]

yah the excitement of today`s exam has decreased the urge for preparing for chemistry..

 

[ibadsiddiqi]

Actually i am quite excited for tomorrow..!!

 

[amazon]

pls solve this qs
A fuel cell uses 240dm3 of hydrogen. Calculate the volume of oxygen and the mass of water formed. All gas volumes measured at r.t.p.
this is from J03.
A comprehensive explanation required. Cant understand the volumes

 

[ibadsiddiqi]

@amazon
is that the entire question? Can you please post the link?

 

[ibadsiddiqi]

i know we have the percentile system in these exams but i heard from a few people that the percentile system is not there in chemistry and biology. Can anyone confirm or deny this??

 

[no.mercy]

@ibadsiddiqi percentile is not there only in maths..

Can someone tell me the chemical test for water?

 

[amazon]

Here

B8

 

[ibadsiddiqi]

you had anhydrous copper (2) sulfate. This is a white powder which in the presence of water turns blue and forms hydrated copper 2 sulfate.

 

[no.mercy]

you had anhydrous copper (2) sulfate. This is a white powder which in the presence of water turns blue and forms hydrated copper 2 sulfate.

is this the chemical test for water?

 

[ibadsiddiqi]

yea!

 

[ibadsiddiqi]

@ amazon
the overall reaction is 2H2 +O2--->2H20
the ratio of hydrogen to oxygen is 2:1. Therefore 240 dm3 of hydrogen reacts with 120dm3 of oxygen.
now, 120dm3 of oxygen is being used. So therefore the number of moles of oxygen being used is 120/24 (volume= no. of molesx 24dm3) = 5 moles.
5 moles of oxygen is are being used. The reacting ratio between oxygen and water is 1:2. so 5 moles of oxygen produces 10 moles of water. Using the formula no. moles=mass/Mr. you calculate the mass of water being formed. Mr of water is 18 and number of moles ( calculated earlier) is 10. So mass=10x18=180g
hope this helped!

 

[amazon]

Awesome explanation. Thanks a million

 

[ibadsiddiqi]

No problem mate

 

[ibadsiddiqi]

Anyone has any idea of the imp topics that shud be revised right now? I mean those topics which are highly expected to come?

 

[superfly]

can someone please explain the fuel cell and the making of slphuric acid. thanku!

 

[ibadsiddiqi]

A fuel cell is a device which as the name suggests, uses a fuel to generate electricity. A common fuel cell is a hyudrogen and oxygen fuel cell in which energy is released by combining the two reactants to form water.
Sulfuric acid can be made by contact process.
i) Sulfur is burned in air to form sulfur dioxide. S+O2--->SO2
ii) Sulfur Dioxide and air are passed over vanadium(V) oxide catalyst at about 450*C to produce sulfur trioxide. SO3+O2--->SO3
iii) Sulfur trioxide is first dissolved in concentrated sulfuric acid to form oleum H2S2O7 and then oleum is diluted with water to produce concentrated sulfuric acid.

now the thing is that Sulfur trioxide can be added to water directly to form sulfuric acid but this is not done as it produces a large cloud of sulfuric acid mist which is corrosive pollutes the air.

Hope you understood

 

[Silent Hunter]

POLLUTES THE AIR AND IS DIFFICULT TO REMOVE TOO

 

[superfly]

what electrolyte is used in he fel cell?

 

[ibadsiddiqi]

sulfuric acid or any other electrolyte which produces oxygen and hydrogen at the electrodes...i think...anyone please correct me if i am wrong.