chemistry p22

[reh2300]

oh wait my molecular formula was C2H4O2

 

[Emily793]

thats correct got that too. mr was 59.9 round it to 60 to get molecular formula... as for the enthalpy thing i calculated the individual masses is it valid??

 

[reh2300]

i did the same i calculated the mass :S i am not sure if its valid but will i get any mark by error carried forward?
and to convert the energy to KJ we had to divide it by 1000 right?

 

[lychee26]

well what i did was, i multiplied heat capacity into 30 and change in temperature. My first delta T came positive so delta H would obviously be negative. How did you find delta H? And yes we had to divide by thousand.

 

[reh2300]

i found out the no. of moles den multyplied it with Mr to find the mass and used dat in the formula :S i dunno y i did all that :S

 

[lychee26]

ohh dont worry that would be ecf. Max you ll lose 1 mark or 2

 

[lychee26]

i found out the no. of moles den multyplied it with Mr to find the mass and used dat in the formula :S i dunno y i did all that :S

HOW DID YOU FIND DELTA H?

 

[heroism999]

for endothemic rxn we should take 15 cm^3 volume as 1 mol of hcl reacted with 1 mol of water...

 

[anahita16]

Holy shit! i made a mistake in using the calculator and ended up with n=3. That's how many marks gone?

 

[notgeek]

i got decomposition enthalpy as +79 kJmol
i think it was 32.6+(2*23.2) = 79....

 

[shressubha]

Got enthalpy as +79 kJ per mol.

 

[shressubha]

oh wait my molecular formula was C2H4O2

I got the same :Yahoo!:

 

[shressubha]

For last question : the compound needs to b reacted with HBr (which cud b obtain from NaBr and conc H2SO4) or any hallides .Then use NH3 in ethanol to substitute halogen. And lastly oxidise the intermediate with any oxidising agent...

 

[lychee26]

hey guys wernt we supposed to multiply with the the mr ? To find delta H. Because there is a similar kind of question nov 03 and they found the delta H by multyplying with the mr.

 

[lychee26]

please tell me.

 

[notgeek]

i duno

 

[notgeek]

molar enthalpy was 60

 

[lychee26]

what did you do?

 

[ying27kia]

hey guys wernt we supposed to multiply with the the mr ? To find delta H. Because there is a similar kind of question nov 03 and they found the delta H by multyplying with the mr.

yes, I did the same way... to find mass it's the most reasonable way
but I still not sure
however will it be ecf on that numb? " just in case it's wrong "

 

[Hsmanime]

Hey, what do you mean by with ecf, max will only lose 1 or 2 marks? Whats ecf mean btw?