Chemistry: Post your doubts here!

[Mahnoorfatima]

http://www.sheir.org/a-level-chemistry-13-nov2010.pdf
Question 25 why not A??
And in 12 my ans is A?

 

[Metanoia]

I end up with 6 :s

Thats the wrong answer? Which year is it?

 

[Metanoia]

http://www.sheir.org/a-level-chemistry-13-nov2010.pdf
Question 25 why not A??
And in 12 my ans is A?

Q12
heat absorbed by 200 g of water = 200 x 4.2 x 48 = 40 320
heat released by 1.6 g of fuel = 40320/45 x100 = 89 600
heat released by 1 g of fuel = 89600/1.6 = 56 000

Q25. Option A can give both aldehyde and acid.

 

[Metanoia]

what are the intermediates for each?

Q16. Barium sulfate is not soluble in the acid, whereas barium carbonates reacts with the acid to form a soluble barium compound.

Q26. X represents a halogen atom.
W: CH3CH2XCH3
X: CH3CH(OH)CH3X
Y: CH3CH2XCH3
Z: CH3CH2CH2OH

 

[nehaoscar]

Doesn't Selenium also have 6 unpaired electrons??
So does chromium ... B is correct but then what about D?

 

[nehaoscar]

Ok so using pv=nRT ... I'm getting 60000K .... Answer is B.... How??

 

[princess Anu]

Thats the wrong answer? Which year is it?

its correct but i don't really know how to do this
its N2014/11

 

[Metanoia]

View attachment 54141
Doesn't Selenium also have 6 unpaired electrons??
So does chromium ... B is correct but then what about D?

Can you type out the spdf configurations of the mentioned atoms?

View attachment 54142

Ok so using pv=nRT ... I'm getting 60000K .... Answer is B.... How??

What values are you using? Chances are you didn't convert dm3 to m3.

 

[princess Anu]

Q16. Barium sulfate is not soluble in the acid, whereas barium carbonates reacts with the acid to form a soluble barium compound.

Q26. X represents a halogen atom.
W: CH3CH2XCH3
X: CH3CH(OH)CH3X
Y: CH3CH2XCH3
Z: CH3CH2CH2OH

why is barium sulphate not soluble in the acid? ://barium sulphate in hydrochloric acid shud form barium chloride which is soluble ,no???

Q16. Barium sulfate is not soluble in the acid, whereas barium carbonates reacts with the acid to form a soluble barium compound.

 

[nehaoscar]

Can you type out the spdf configurations of the mentioned atoms?



What values are you using? Chances are you didn't convert dm3 to m3.

Oh you have to use spdf!? Selenium is in group 6 which shows it's short of 2 electrons right? so i just assumed that means it has 6 unpaired electrons
Ok so by using spdf it shows that selenium doesn't have unpaired electrons

And for the second Q
I'm using these values

pv = nRT
(1 x 10^5) x (1.247 x 10^-1) = (6.35 / 253.8 ) x 8.31 x T
so T = 60000K

So what values are wrong??

 

[nehaoscar]

How are there 3 cis-trans isomers

 

[Metanoia]

why is barium sulphate not soluble in the acid? ://barium in acid shud form barium chloride which is soluble ,no???

solubility rules, BaSO4 is insoluble.

Hmm.. Which reaction are you basing on when you mention barium sulfate and acid?

 

[Metanoia]

Oh you have to use spdf!? Selenium is in group 6 which shows it's short of 2 electrons right? so i just assumed that means it has 6 unpaired electrons
Ok so by using spdf it shows that selenium doesn't have unpaired electrons

And for the second Q
I'm using these values

pv = nRT
(1 x 10^5) x (1.247 x 10^-1) = (6.35 / 253.8 ) x 8.31 x T
so T = 60000K

So what values are wrong??

volume needs to be converted to m3.

 

[nehaoscar]

volume needs to be converted to m3.

Oh i see! i just divided by 10 from deci to meter ... didn't cube it!
Thankyou

 

[princess Anu]

barium sulphate with the acid found in stomach.. ( HCL)

solubility rules, BaSO4 is insoluble.

Hmm.. Which reaction are you basing on when you mention barium sulfate and acid?

 

[princess Anu]

solubility rules, BaSO4 is insoluble.

Hmm.. Which reaction are you basing on when you mention barium sulfate and acid?

Solubility rules apply to all solvents? be it acid, base etc? :O

 

[nehaoscar]

Someone please show me the redox changes for these...
correct is 2 and 3

 

[Metanoia]

Solubility rules apply to all solvents? be it acid, base etc? :O

If the solid reactant is not soluble in water itself, it would be observed to "dissolve" when it can react with acid to form a soluble salt.

Solid reactants "dissolving " with acids commonly follow these reactions
Base (s) + acid
Carbonate (s) + acid
Metal (s) + acid

BaSO4 belongs to none of them.

 

[Metanoia]

View attachment 54144

How are there 3 cis-trans isomers

Draw the isomers that you have, likely you have 2 of the same kinds.

 

[nehaoscar]

How is this called ethyl butanoate?
It has 6 Carbon atoms .....