Chemistry: Post your doubts here!

[mehria]

w09 qp 21 q1(d)

it's so cnfusing :/

 

[princeali97]

it's so cnfusing :/

I know right!

 

[Jelleh Belleh]

well reaction 4 shoows an addition reaction and in an addition reaction always one product forms so we can say its the addition product

But the product in reaction 4 is CH3C(OH)(CN)CH3, not CH3COCH3.

 

[mehria]

w09 qp 21 q1(d)

oh ...the thing is that here we r removing 2 electrons at one time so the first ionisation energy + the second ionisation energy will give us the total energy required to remove 2 electrons from a barium atom... as down the group ionisation energy is decreasing and I.E of radium will be less than Ba so we will write a value that is lower than the value for Ba...

 

[princeali97]

oh ...the thing is that here we r removing 2 electrons at one time so the first ionisation energy + the second ionisation energy will give us the total energy required to remove 2 electrons from a barium atom... as down the group ionisation energy is decreasing and I.E of radium will be less than Ba so we will write a value that is lower than the value for Ba...

hmmmm..i got it! yaaay! thank you.I wasted 30 mins on this question.i didnt see that 2 electrons are being removed from Ra .Good thinking.
Thanks!

 

[mehria]

hmmmm..i got it! yaaay! thank you.I wasted 30 mins on this question.i didnt see that 2 electrons are being removed from Ra .Good thinking.
Thanks!

lol... no problm

 

[Marwaa]

did someone understand m/j 2011(paper 22) question 5(C)? can you explain how you get the answer?

 

[Namehere]

among all salts in our syllabus the only insoluble salts of Barium are Barium Carbonate, BaSO4 and BaS03
we will first add HCl to remove carbonate and then add BaCl. if we get ppt then we add dilute acid in excess to make sure it is SO4 not SO3.
BaSO4 is insoluble in acidic solution.

Suchal, would you mind giving me a list of what are we supposed to know what is insoluble and what is soluble (like a generalisation). Thanks!

 

[Jelleh Belleh]

did someone understand m/j 2011(paper 22) question 5(C)? can you explain how you get the answer?

Just draw the structural formula of the trans isomer of the given formula.

 

[Marwaa]

Just draw the structural formula of the trans isomer of the given formula.

yeah but why is that the answer? i can look at the marking scheme and it would tell me the same thing. i don't understand why

 

[Jelleh Belleh]

yeah but why is that the answer? i can look at the marking scheme and it would tell me the same thing. i don't understand why

It says right there in the question that elaidic acid is the trans isomer of the formula, so just draw it.
The aim of this question was to test whether or not you know how to draw a cis isomer and a trans isomer.

 

[saadgujjar]

plz guide me about paper 5.....rate of reaction question in may june 2007...plz anyone explain me in detail..plz scan if any one has solved this question

 

[Suchal Riaz]

Suchal, would you mind giving me a list of what are we supposed to know what is insoluble and what is soluble (like a generalisation). Thanks!

all nitrates are soluble
all group 1 carbonates are soluble
group 2 carbonates are insoluble
most of the ammonium salts are soluble.
oxides of metal depend on the reagent they are dissolved in. like CuO is soluble in NH3 solution but insoluble in NaOH solution.
most sulfates are soluble. but BaSO4 is insoluble.
most halides are soluble except silver hallides. and their solubility depends on the medium as well.
AgCl is white ppt.
full list + general trends: http://www.chemguide.co.uk/inorganic/group2/solubility.html​

 

[sohaibakram92]

Can anyone please post worked solutions of paper2 and paper4!

 

[sohaibakram92]

Re: All Chemistry help here!! Stuck somewhere? Ask here!

These sites might help ... check em

1.Beta-Theta.com Chemistry Section
http://adf.ly/378ET
Notes on a number of topics relevant to AS/A Level Chemistry are included. The notes include a particularly good interactive Periodic Table. There is also access to Homework Help and to a Midnight Café chat-room.

2.http://adf.ly/l8tn
This is a US site intended for first year undergraduates, but much is relevant to AS/A Level Chemistry. Notes, articles and tutorial are included. A number of experiment simulations can be accessed. The compound library is very good.

3.http://adf.ly/l8to
A lighthearted look at many aspects of Chemistry. There are a lot of links to useful pages written by teachers and students. Not all of this is relevant to AS/A Level, but much is. A wealth of information and a lot of fun.

4.Chemsoc Interactive Periodic Table
http://adf.ly/l8tp
A high quality interactive Periodic Table with photographs and information about each element.

Entirely BOGUS SITES NOT A HELP TO ANY ONE!!!!

 

[Mohammed salik]

Entirely BOGUS SITES NOT A HELP TO ANY ONE!!!!

These were posted three years Ago!!

 

[Abdulaziz T]

chem p5: I need help in oct/nov 2012 paper 51 Q1 plzzz

Hope you guys reply cuz there's no time Thanks

 

[Ameena Eesa]

Aswk. In electrolysis, the metal ions travel from the solution to the cathode or from the anode to the cathode? What's the purpose of keeping the metal ions in both places? Plz help.

 

[Ameena Eesa]

Can you describe how electrical energy can be produced from simple cells?

 

[saniyaaamir]

Guys can nabh4 convert an
acid into an alcohol?