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Chemistry: Post your doubts here!

DragonCub

DragonCub

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hihi said:
Does it have to do anything with d+ and d- ...
Click to expand...
No, it's totally irrelevant. What determines the chiral centre are four groups with different atoms or structures, not with different relative charges.
hihi said:
and when calculating enthaply change for example in reaction : Ca(s) + 2H2O(l) = Ca(OH)2 (aq) + H2 (g) and u r given Q, which moles do u take from Ca or H2O ?? :D Thanks so much
Click to expand...
Mole of Ca or mole of H2.
In fact, the equation must first be stoichiometrically balanced (balanced to smallest possible integers), and then calculate the resultant enthalpy change. For example, A and B react to from C and D. Even if the balanced equation is 9A + 11B = 12C + 10D, it is still balanced to smallest integers. Enthalpy change (per mole) is still the total change according to this equation.
So the enthalpy change is more like the change "per balanced equation". :D
 
DragonCub

DragonCub

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hassam said:
it shud not be molecular ion i guess....thats inappropriate word
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I remember that in IGCSE Chemistry textbook the ions consisting of groups of atoms are called molecular ions, like SO4(2-), CO3(2-), NO3(-) and NH4(+). The complex ion is quite similar. Or should we call it "multi-molecular ion"? :p (Just kidding)
 
usmiunique

usmiunique

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ASA,
Can anyone explain the chromatography thing? like what is the stationary phase? what is the mobile phase? what are the two types of seperation techniques used in chromatography, like adsobtion and partition?
I have read it many times in the support booklet and in Chemguide but still can't understand it.. any help would be greatly appreciated!
 
usmiunique

usmiunique

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hassam said:
why we acidifiy solution containig fe 2+ ....when trying to dtermine its conc.
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we determine the conc. of fe2+ by titrating with MNO4- ions and the half eqn of MNo4- ions is
MnO4- +8H+ +5e- -------->Mn2+ +4H2O
this eqn has H+ ions.. which are supplied by the acid when it ionises it solutions!
 
hihi

hihi

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DragonCub said:
No, it's totally irrelevant. What determines the chiral centre are four groups with different atoms or structures, not with different relative charges.

Mole of Ca or mole of H2.
In fact, the equation must first be stoichiometrically balanced (balanced to smallest possible integers), and then calculate the resultant enthalpy change. For example, A and B react to from C and D. Even if the balanced equation is 9A + 11B = 12C + 10D, it is still balanced to smallest integers. Enthalpy change (per mole) is still the total change according to this equation.
So the enthalpy change is more like the change "per balanced equation". :D
Click to expand...


Thank you so much !! :)
 
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